I'm very new to RU, so could someone please explain to me why Blastoise is sub-par in this meta? Thanks!
Compared to the other viably possible spinners in the tier (Dhelmise, Donphan, Torkoal but its not spinning in reality, Cryogonal), it mainly lacks presence, and so is an empty shell. You might think it's good when you add other moves on like Scald and Toxic, Roar, Haze, Refresh, Counter, and so on with that spinning, going "oh, its bulky and it checks this, and 100% scald burns is soooo good". A lot of ladder players probably have this thought as well, as it got into RU for some reason.
Donphan checks Doublade, a common defensive setup threat, and can spin on Registeel/Bronzong while threatening Ghost spinblockers with Knock Off; Dhelmise can punch holes in teams, trap, setup or spin, and so can be a surprise with what you give it and therefore scary unpredictable; theoretically if Torkoal was spinning, the Drought boost gives it a good damage output and can SR for you, and should it not be able to handle what it's weak to it can pass that job on to its Grass Chrolophyll teammate to break open a chance for it. Cryogonal has a passable SpAtk to use that threatens premier Spikers Chesnaught and Roserade while giving opposing defoggers a hard time with Freeze Dry, and has an immunity + very good SpDef to take advantage of and switchin (sounds better on paper but pretty meh lol). The important thing with these four is that they have options or attributes that give them a consistent amount of opportunities to spin while also being threatening in some form.
Blastoise is a completely defensive spinner with 4 slot syndrome that's easily taken advantage of with threats like CM users in Reuniclus and Comfey, Lax, Heracross, Growth Venusaur in Sun, Dragalge, and Shaymin. Rapid/Scald/ Toxic/Filler is the usual set, and if you're gonna use I would make the last slot Roar so it at least isn't complete bait while phazing for you (
http://prntscr.com/fra357 for other options). Otherwise, its very hard to justify a reason why to at least use it over the other three, or any other removal for that matter.