>>29878013They are not that good, but they are good enough that every team will need at least 1.
However, it's not like M-Salamence where they have no weaknesses. Each of the allowed legendaries has a downside.
The island guardians have limited movepools and none of them learn play rough. Tapu Bulu doesn't get a fairy STAB.
Nihilego isn't dangerous, 4x weak to ground with shit Def stat (EQ bait).
Buzzwole is slow and has very bad special defense and special attack (also doesn't learn a single physical Bug STAB)
Pheromosa is the most troubling, with U-turn, Brick Break, Ice Beam, Return. But again, although it has good coverage, it has a limited and predictable movepool so you can plan around it. She doesn't have access to a single bug STAB that lets her stay on the field, just U-turn shenanigans. It also dies to priority moves because of very low defenses, it is too frail to exist in the Doubles meta I think.
Kartana will require teams to bring Fire special attacks, but even Chansey (base 35 special attack) with no investment in special attack has a 31% chance to OHKO Kartana with Flamethrower. Kartana also has only Physical damage because its special attack is low, so it can be planned around. It also doesn't learn any Steel-type moves at all so it only has Grass STAB. Its effective movepool is only this: Leaf Blade, Sacred sword, Air Slash, Night Slash, Return, X-Scissor. Decent coverage, but doesn't get STAB on any of the good moves.
Xurkitree is slow and cannot do anything to LightningRod pokemon. Also dies to priority.
Celesteela has a bad movepool.
Guzzlord has probably the best movepool out of the bunch and will be one of the better Ultra Beasts, but it's still slow and has low special defense (dies to moonblast and dazzling gleam).
The Ultra Beasts and the Tapus check each other, and none of them on their own are extremely dangerous or impossible to deal with. It will take a smart player to use them to max effect, unlike M-Salamence
