Trust me, letting in Zama is not good. It is a really great mon, the id set destroys teams that have ghost types even a bit chipped. The counterplay to Zama is don't let it in for free or setup for free, Garg is a free entry and setup. The salt cure chip is annoying, but dealable with. Again, corv forces a recover, it will bp once, doing 30%, and then 15% with the next one. Garg has to recover off that damage, letting you reposition.If you have Zam counterplay, letting it in isn't that big a deal. Regarding Corv, like I said it's free boosting for Garg while Corv does nothing to it really. Corv can try ID back but you aren't winning a 1v1 generally and you burn a lot of roosts potentially. You don't want to stay in and try to attack it when you'll be forced to burn so much recovery into it.
Block Garg can be more match up heavy, but it also can still work vs non stall teams depending on structure (so yes match up). But typical block Garg are tera ghost+curse which trap almost anything and removes them with ghost curse+salt.
It was UUBL for so long because ladder tends to take way longer than it should to catch onto meta trends. Even before it rose Garg was going strong for quite a bit there. It's not autopilot and requires more care than it used to when building with and around it, but it's also not really difficult to "execute". The power of its chip and progress forcing is useful almost guaranteed most of the time. I'm not really sure what "passively swith between defensive mons" is supposed to be, considering that for slower teams there isn't much an option beyond trying to stall out Salt Cure, as they kinda struggle to scratch it. It's an A rank mon minimum right now, not A-. It's strong and to a point where people are starting to prep for it seriously again.
On the note of Garg, I love this set.
Garganacl @ Leftovers
Level: 100
Careful Nature
Tera Type: Water
Ability: Purifying Salt
EVs: 252 HP / 52 Def / 204 SpD
- Salt Cure
- Protect
- Recover
- Curse
This set, when certain checks are removed, can potentially solo endgames by itself without needing another attack due to the longevity of recover+protect and eventually, boosted Salt Cures are too much along with their added chip. This here is a fun game illustrating the power of curse Garg where after Tusk was KOd, Garg was able to come in at turn 19 and proceeds to never switch out again and slowly accumulate boosts to win by itself, beating a double regen core along with Meow. It also highlights why Curse+Salt is great as it abuses slow pivoting regen mons attempting to soak the hit for teammates and slow pivot out, allowing Garg to get lots of chip on everything.
The block curse thing is definitely cool, I thought you were using normal moves but ghost curse is interesting. That definitely makes it a lot more threatening.
I also stated that it is OU material, but again, I can see why it was UUBL. It is difficult to use because it lets in a ton of massive threats. That means that it can't be self sustaining i.e. it NEEDS teammates. Even things it should beat, such as ghold, it has to be careful around due to it's power. Slower teams need to have firepower, unless they are stall in which case can use other methods to play around it. In this meta, you cannot be passive, that is something people do far too often. If you try to do that, you will get bowled over by many setup sweepers easily such as volc, gambit and gouging, compared to where you normally would have a chance against them. A common thing I use in team building is have one band/specs user, that decreases the teams passivity a lot. Garg again, takes advantage of passive teams. That's my whole point great mon, but it's a bit of a skill check. It can still work well, if supported well, but that's not a A rank mon to me. Maybe you disagree, but it's along the lines again of clefable and dondozo. Clefable can decimate teams that rely on passive damage, but can struggle with high power attacks. Dondozo prays on teams that rely on physical attackers, but any special attackers decimate it. With support, they can be amazing, but they can't do it solo. Compare that to A rank or A+ rank mons, who can more or less function separately, and Garg is more along the lines of A- rank.