Some post UMPL thoughts:

Calyrex-I is a menace in the builder and essentially mandates that every balance / BO have a tera water or risk getting absolutely steamrolled by it. It's not actually that good once it runs into that tera water fairyceus, but if you manage to bait out tera with something else, Caly-I can get really scary, really fast, especially since it's essentially impossible to OHKO. I'm not convinced that fullroom is any good since it mostly just exacerbates the aforementioned water issues but right now, Caly-I is an excellent breaker for bulky offense.

NDM is in a really weird place right now. It's extremely difficult to just put on teams, but it feels really good into a lot of the fairyceus structures that have been so popular recently. Its biggest drawback is probably that it pretty much requires tera to avoid getting statused, but if it manages to find a few setup turns, it's really, really scary. At the same time, if there's a waterceus, you might as well just forfeit immediately. NDM also has a really hard time breaking through the omnipresent Ting-lu and really wants covert cloak for Ho-Oh, but can't run it without getting chipped to death (enter hatterene). In practice, I think right now it fits best on bulkier balance teams that can provide enough of a defensive core to reduce reliance on dusk mane's defensive capabilities and save it for a sweep, but even there, it's difficult to justify over alternative sweepers like bulk up ekiller. Overall, I think dusk mane gets more hate than it deserves and it's definitely still usable and even good on occasion, but it's definitely fallen on hard times.

You gotta have it. No-lu BO structures can get pretty scary but as soon as they run into specs caly or mirai or, god forbid, a mirai and a caly, their defensive backbone tends to implode and they lose really fast. Lu's still just as vital as ever on anything other than hard stall or hyper offense and its place isn't changing. Lu doesn't like the Caly-I has been getting more popular, but it also only really belongs on teams that have other checks to caly-i, so it's not the end of the world.

Man, groundy's in a weird spot. It's so hard to fit it on standard balance / bulky offense structures because those want a physdef arc and an ekiller, and groundy's a really bad physdef arc right now because it's weak to caly-i and takes neutral damage from everything korai throws at it. At the same time, cm groundy is an excellent win condition, so teams can still make space without seriously jeopardizing the caly-s matchup by dropping an ekiller for a ho-oh, or by running kyogre as a backup check to caly-i. You can also slot in Ho-Oh as an alternative to fairyceus while still running ekiller, but doing so makes it even harder to handle caly-i. DD groundceus is, of course, just as broken as it's always been on offense. Overall, groundy's really good, but building with it on balance / BO forces some pretty unpleasant compromises and ensures that the matchup against one caly form or the other is going to get quite a bit worse.

Waterceus continues to play second fiddle to fairy as a defensive arc form, but I think its use has picked up somewhat as caly-i has grown more popular, since it can reliably check caly-i without having to burn tera. It's also a lot more reliable against Zacian-C, but continues to suffer from not resisting Koraidon's STABS, which means that it's liable to get chipped very quickly, especially if spikes are up (enter hatterene). Regardless, Dragon Tail offers a lot of utility as an emergency check to cm arcs or to, say, tera fire ekiller while also letting it rack up spikes damage on opponents and providing a useful way to punish attempts to bring in miraidon. Waterceus is probably happiest on either fatter teams that can afford secondary koraidon checks or more offensive teams that apply enough offensive pressure to keep hazards off so it can't get 2hkoed. Also of note is its ability to pretend to be a backup kyogre check, which can be useful if you really, really expect them to click ice beam. On the other hand, it can't do much back, so it's most useful against the admittedly rare choice kyogres.

lol I think this went like 5-0 in umpl or something. It's really, really hard to build around but when you get it on the right team things just work. It's also a huge pain in the ass to play well with but it's a funny secondary koraidon check since it takes zero from fighting moves and it also oppresses lu and helps open the door for some weirder teammates that might otherwise suffer from hazards. It also beats standard (no sludge bomb) eternatuses and is a key enabler for (bad) fullroom. CM hatt turns into an amusing win condition on some bulkier stuff since it can heal pretty well with draining kiss and doesn't get ohkoed by a whole lot after a boost. Personally, I like to run enough speed evs on hatterene to outspeed tinglu to make it easier to switch in on it to deny spikes and heal up, but it does take a lot of investment and isn't strictly necessary, especially if you're using it as a TR setter instead. Hatt also offers really nice utility against hyper offense teams, forcing them to lead with awkward mons instead of their suicide leads, and generally denying hazards unless you sack it and play badly. On the other hand, you're essentially playing with a 5 mon team in those matchups, since hatt is deadweight outside of keeping hazards off.
Webs did really well in umpl but I think that's partly an artefact of a lot of teams having to force fairly inexperienced players into the tier, and partly a reflection of the fact that polt is good more than a commentary on the viability of webs as a playstyle, so I don't think it's as broken as the usage stats would suggest. You know what is as broken as the usage stats suggest? Hatterene.

Calyrex-I is a menace in the builder and essentially mandates that every balance / BO have a tera water or risk getting absolutely steamrolled by it. It's not actually that good once it runs into that tera water fairyceus, but if you manage to bait out tera with something else, Caly-I can get really scary, really fast, especially since it's essentially impossible to OHKO. I'm not convinced that fullroom is any good since it mostly just exacerbates the aforementioned water issues but right now, Caly-I is an excellent breaker for bulky offense.

NDM is in a really weird place right now. It's extremely difficult to just put on teams, but it feels really good into a lot of the fairyceus structures that have been so popular recently. Its biggest drawback is probably that it pretty much requires tera to avoid getting statused, but if it manages to find a few setup turns, it's really, really scary. At the same time, if there's a waterceus, you might as well just forfeit immediately. NDM also has a really hard time breaking through the omnipresent Ting-lu and really wants covert cloak for Ho-Oh, but can't run it without getting chipped to death (enter hatterene). In practice, I think right now it fits best on bulkier balance teams that can provide enough of a defensive core to reduce reliance on dusk mane's defensive capabilities and save it for a sweep, but even there, it's difficult to justify over alternative sweepers like bulk up ekiller. Overall, I think dusk mane gets more hate than it deserves and it's definitely still usable and even good on occasion, but it's definitely fallen on hard times.

You gotta have it. No-lu BO structures can get pretty scary but as soon as they run into specs caly or mirai or, god forbid, a mirai and a caly, their defensive backbone tends to implode and they lose really fast. Lu's still just as vital as ever on anything other than hard stall or hyper offense and its place isn't changing. Lu doesn't like the Caly-I has been getting more popular, but it also only really belongs on teams that have other checks to caly-i, so it's not the end of the world.

Man, groundy's in a weird spot. It's so hard to fit it on standard balance / bulky offense structures because those want a physdef arc and an ekiller, and groundy's a really bad physdef arc right now because it's weak to caly-i and takes neutral damage from everything korai throws at it. At the same time, cm groundy is an excellent win condition, so teams can still make space without seriously jeopardizing the caly-s matchup by dropping an ekiller for a ho-oh, or by running kyogre as a backup check to caly-i. You can also slot in Ho-Oh as an alternative to fairyceus while still running ekiller, but doing so makes it even harder to handle caly-i. DD groundceus is, of course, just as broken as it's always been on offense. Overall, groundy's really good, but building with it on balance / BO forces some pretty unpleasant compromises and ensures that the matchup against one caly form or the other is going to get quite a bit worse.

Waterceus continues to play second fiddle to fairy as a defensive arc form, but I think its use has picked up somewhat as caly-i has grown more popular, since it can reliably check caly-i without having to burn tera. It's also a lot more reliable against Zacian-C, but continues to suffer from not resisting Koraidon's STABS, which means that it's liable to get chipped very quickly, especially if spikes are up (enter hatterene). Regardless, Dragon Tail offers a lot of utility as an emergency check to cm arcs or to, say, tera fire ekiller while also letting it rack up spikes damage on opponents and providing a useful way to punish attempts to bring in miraidon. Waterceus is probably happiest on either fatter teams that can afford secondary koraidon checks or more offensive teams that apply enough offensive pressure to keep hazards off so it can't get 2hkoed. Also of note is its ability to pretend to be a backup kyogre check, which can be useful if you really, really expect them to click ice beam. On the other hand, it can't do much back, so it's most useful against the admittedly rare choice kyogres.

lol I think this went like 5-0 in umpl or something. It's really, really hard to build around but when you get it on the right team things just work. It's also a huge pain in the ass to play well with but it's a funny secondary koraidon check since it takes zero from fighting moves and it also oppresses lu and helps open the door for some weirder teammates that might otherwise suffer from hazards. It also beats standard (no sludge bomb) eternatuses and is a key enabler for (bad) fullroom. CM hatt turns into an amusing win condition on some bulkier stuff since it can heal pretty well with draining kiss and doesn't get ohkoed by a whole lot after a boost. Personally, I like to run enough speed evs on hatterene to outspeed tinglu to make it easier to switch in on it to deny spikes and heal up, but it does take a lot of investment and isn't strictly necessary, especially if you're using it as a TR setter instead. Hatt also offers really nice utility against hyper offense teams, forcing them to lead with awkward mons instead of their suicide leads, and generally denying hazards unless you sack it and play badly. On the other hand, you're essentially playing with a 5 mon team in those matchups, since hatt is deadweight outside of keeping hazards off.
Webs did really well in umpl but I think that's partly an artefact of a lot of teams having to force fairly inexperienced players into the tier, and partly a reflection of the fact that polt is good more than a commentary on the viability of webs as a playstyle, so I don't think it's as broken as the usage stats would suggest. You know what is as broken as the usage stats suggest? Hatterene.