The main issue with Wartortle is its survivability. The neutrality to Rock doesn't give it the edge over the other two spinners if it can't get rid of that damage. Pairing a Wish user to support Wartortle is also not just impractical, but is much harder than it looks. As a user of Roselia and Frillish, I've great difficulty trying to keep them alive for the match, and these two unlike Wartortle do have ways of recovering their health.
In other words, if a pokemon has to rely on Eviolite to compensate for its bulk, it would have to give up leftovers. These unevolved pokemon had better have acceptable bulk to begin with and enough offensive presence to grant them staying power (and thus less susceptibility to hazards) in order to get the job done. This is why Gurdurr, Misdreavus and Piloswine enjoy much usage and respect whereas Roselia, Frillish and of course Wartortle struggle to do well in their respective roles. (I'd say Metang is somewhere in between, if only because his fantastic resistances are offset by his mediocre HP, unlike Pilo, and lack of recovery)
also for those of you saying that wartortle is setup bait—try setting up on something that carries haze, seismic toss, and scald?
I remember stating that Roselia gives no shits about what Wartortle does, which kind of baffles me how Wartortle usage is above
Roselia's. Let's not forget the fact that Wartortle is tremendously susceptible to status, which can easily affect how well he performs. Substitute users in general can still have their way with Wartortle by dancing around status/Scald with Sub and attack/boost when a Seismic Toss is coming. This is especially true for those with super effective moves and/or recovery. The fact that Wartortle has those moves can lure an inexperienced player to try and fend off the opposing threat when they shouldn't. Wartortle can
fight back against some threats, but still doesn't do well against most, hence why it "sucks" (I'd use the term inadequate).
One more thing: no matter what moveset Wartortle runs, it will always be setup bait for to many things. No Toxic? Attackers/Boosters with almost any form of recovery will beat you hard. No Seismic Toss? Have fun with Substituters. No Haze? I shouldn't explain this to anyone about what will happen, whereas no Scald leaves you helpless before any Ghost type (and even then, Scald doesn't beat Golurk without burns, not to mention the rare Frillish). Rapid Spin are on 98.174% of all Wartortles. I don't want to know what the remaining 1.826% were smoking.