Originally Posted by Zenithale

That's not the first time I read that, and honestly I don't understand why there are so many people saying Cannon stage ability is useless/bad. Sure, it depend entirely on the map: if there is no cannon that's useless, indeed. But note on map with cannons the ability affect ALL your 5 Teams and is additive (1 ability = 2 shoots, 2 abilities = 3 shoots etc). Much more efficient than a flat +x% Attack/Defense, especially for beginners who don't have 4 strong Teams. Even a weak Team can kill a stronger Boss who has already lost X0% of its Life.
IMO the only completely useless abilities are the [Raid Boss] ones, because Raid Boss are weak and we prefer to poke (more or less hard) them most of the time (else we share them to random players and they will kill them for us very quickly).

As you say, it's not useless but the fact is it's fair to say it's bad due to the rarity of said cannons. It's a niche ability that rarely comes up, and unless your teams are weak (as you mentioned beginners), it makes little difference as your teams can clear maps without too much issue already. It's useful for newbie teams on event maps with cannons, but that's about it.

RB Buffs are silly 99% of the time since the only time they're useful is the super-rare spawned RB events. RB events are probably rarer than stages with cannons and considering the rare spawn is the only one where those buffs could actually mean the difference between killing them or not, their usefulness is damn near 0.