I think that a lot of these things are just not really correct?This thing will probably be pretty niche and I don't see it being terrifically present throughout the meta. Yea the most common Magearna set can't touch it, but also it's just the freest Mag spike ever. Driller works because not only does it blank Mag, it also gets rid of the Spikes that Magearna puts down. As for Clodsire's theoretical ability to blank setup sweepers... I don't really see it. For one, Clodsire isn't walling physical sweepers, of which are currently looking very strong without Lando there to check them. And when it comes to special setup sweepers, we have CM Arceus, Mewtwo, and Emu. In the case of Arceus, Clod either gets taunted, or can't do shit back to Arceus because CM Poisonceus is the best non-taunt CM Arc. CM Taunt Grasseus already uses Tera Poison more often than not anyways so that's one more thing that Clod can't check. Oh speaking of which, more CM pokemon can run Tera Poison now because Scarf Lando-T isn't a thing that exists anymore. And in the case of M2 and Emu, yea you need to spend tera to beat them which imo is kind of a waste of tera. Clod just seems to have a lack of good entry points, and doesn't exactly click the most threatening buttons once it actually comes in, so I honestly don't really see it being that incredible in the current meta.
First off Clodsire also gets spikes so if Mag clicks spikes then Clod Trades those spikes and the Clodsire user is actually better off most of the time since Mag doesn't usually run Heavy-Duty Boots. This means you are constantly winning off that interaction and it can serve as a way to punish Mag entry points (Like say, with Urshifu-Dark's U turn) to force cheap damage into it and set constant Hazards
You also forgot about the top #2 usage mon, Terapagos, who is a special sweeper who gets completely shut down by Clodsire in every way. As much as it is a spinner, it is also a sweeper without any form of recovery who gets checked by Toxic even in non-unaware sets. Additionally, It beats any Non-rest form of Giratina. I've seen a lot of people drop rest nowadays in favor of playing it without recovery and relying in its natural bulk or Alomomola to check things...which means that a toxic landed on a Giratina will put it in a timer forever, This basically means Clodsire beats the two best forms of Hazard control. which is an important task for any hazard setter.
Clod's access to every hazard gives it unmatched versatility and overall its most likely the best Stealth rocker who actually wants to run the move in the tier at the moment, as the only other Uber options are either Arceus (would rather run any other move), Landorus-I (why are you giving up a move on this wallbreaker, you are handicapping it for very little gain), and Terapagos (Which is pressed for moves and its support set is very mediocre). The rest of the options are either too niche (Dialga) or don't fit the pokemon's niche (Deoxys, Annihelape). Of the OU rock setters, there is only great tusk (who is very mediocre overall), Garganacl (my goat), Clefable (probably reserved for stall only) and deoxys speed (HO exclusive). Stealth rock access is key now that Landorus-T has left the tier, so Clodsire has quite literally the best button to click every time it comes in. Access to toxic is also really rare and it smacks all the toxic immunites for good damage besides Balloon Gholdengo and Corviknight.
Clodsire might get taunted but if it is running Poison Jab and lands a poison it is very likely Clodsire 1v1s most Arceus if it has a resistant tera, altough this is only an option for stall (but this is still a huge deal for stall since it means that Stall doesn't get 6-0'd by Arceus-Dark anymore)
You talk about Cmers running Tera poison...which Clodsire will smack for good damage because it has STAB Earthquake. It might not deal the biggest damage but getting 3hkos is big when the opponent will 4hko you is important.
I don't think Clodsire is going to be a top 10 mon overall...but I genuinely think you are underselling its qualities. It is significantly better than you made it sound here, considering the fact that it counters the top two mons (Mag and Terapagos) and it smacks the third with hazards and STAB Eq. Arceus-Poison might wall it but it also doesn't want to swap into it repeatedly due to it being 3hko'd by EQ and not having access to boots. It has fantastic match ups into a lot of the tier, and it brings stability to HO match ups with access to Tera Dark (Espathra users in shambles).
Also just throwing my hat in the ring, I think that it is possible we see an increase of more offensive Mags. Still same set as before (Fleur Volt Spikes) but with offensive leaning EVs. The main reason why I think this is the case is because there are not many mons Mag needs to wall at the moment, and most of the ones it walls are possible to cover with other teammates (Urshifu dark and Sneasler can be covered easily). A more offensive leaning EV spread can help Mag with less passivity and allow Mag to actually threaten a lot of things (Mainly things like Arceus-dark). If it starts running a spdef EV spread it can also live an Earth power from Landorus-I at full and then Ice beam it to death, which is a neat thing.