i get where you are coming from saying tangrowth is an easily predicted mon. like most defensive pokemon, you can usually lure it in with a breaker that only it walls, such as when you have zygarde out vs. something and your opponent's only zygarde SI is tangrowth. however, what makes tangrowth a lot less passive than other defensive pokemon is regenerator. even if this happens, in most cases you can just switch again and gain some HP with tang. also, this really puts things into a vacuum: predictability is dependent on the player. i don't know about most people, but when i make VR posts, i generally try to make them under the lens of me playing against a player of equal or greater skill. if i'm playing someone way better than me, then yeah they'll probably get the reads right every time and tang will be useless, but this is a poor argument because it can be said about virtually every pokemon.
regarding tang being passive: for a defensive pokemon, it isn't that passive at all. the combination of regenerator, decent offensive stats, and a pretty wide offensive movepool means it doesn't just sit there like clefable, toxapex, or gastrodon. this is why it's super nice on bulky offense teams: it's a fatmon that can counter a LOT of things really reliably, but it does it without sapping as much momentum. regenerator means you can make double switches to strengthen your wall. it isn't really set up bait because, unlike clefable, it isn't compromised if something that sets up on it comes in. thinking in somewhat of a vacuum: if your clef is low (say you took a zen from a medi and you moonblasted) and something that can set up on it comes in, your clef is now really low, meaning it'll probably be pretty tough to get in on something and heal, making your clef a lot less useful. with tang, you can just switch out vs. that thing that it is set up bait for, making it a bit more useful. this isn't to compare tang and clef since they aren't really interchangeable; i'm just pointing out why tang isn't passive, hence why it is seeing more and more usage on bulky offensive teams.
this also isn't just about grass typing, though i do think tang is second to bulu as a "defensive grass" in the tier. neither of these wall protean greninja because those commonly run gunk shot and/or ice beam now. ice ash greninja is worth mentioning given it seeing a bit more usage than before recently, but it's still a fairly niche choice that isn't prevalent enough to consider that strongly (yet). this isn't to purely look at the VR; not too long ago amoonguss was pretty low on the VR and now it's sorta in the middle because people saw how nice the AV set could be (not as much nowadays). however, i think there's a reason why tangrowth with regenerator has always been so good, and there's a reason it has consistently been at its peak in bulky offense centric metagames. the meta is currently seeing a bit of a boom in bulky offense teams, tangrowth both fits nicely on these teams and acts as an answer to things these teams commonly run (zygarde, ash greninja, tapu koko, specially defensive sd tapu bulu, etc.), and the VR thread is largely centered around the metagame. as a result, it'd make sense for tangrowth to rise... it is a really good meta pick right now.
