Why is Dragapult in OU? It's literally a Pseudo-Legendary and can easily wipe out teams with just a Dragon Dance set up. I feel like it could be an Uber like Galarian Darmanitan, but I'm just asking.
You might be surprised to hear it, but Dragapult isn't actually all that exceptional as a Dragon Dance sweeper.
The thing about Dragon Dance is that Dragapult's Speed is already high enough that the boost doesn't really mean much - all it achieves in context is outspeeding Zeraora and scarfers (and it's still weak to some priority moves in Sucker Punch and Shadow Sneak) - so against the majority of opponents, it only comes down to a one-stage Attack boost. For that matter, its high Speed and mixed offenses account for so much of its BST that it's actually on the frail side and it can be hard to set up in the first place, to the point that any opponent it doesn't knock out in one hit will easily finish it off.
It also doesn't even have a usable physical Ghost STAB, to the point that its standard Dragon Dance set includes a Dragon STAB and then, for coverage moves,
Steel Wing (which is
very weak - the main reason it outdamages Dragon Darts on Fairy-types is because Dragon Darts
doesn't work, and it's not worth using otherwise even if it's super effective) and also a
special move (which doesn't even benefit from Dragon Dance). Dragon Dance Dragapult can be effective as late-game cleanup, but it's not cleaving through any teams unless its allies have significantly weakened them already.
For reference, it's actually considered more effective to use full special attacking sets on Dragapult - and those are
good, which is why it's OU at all, but that relies on its base 100 Special Attack and isn't supported by any relevant boosting moves, so it's a far cry from how strong its physical sets looked to you. (For reference, the actual niche of special sets seems to be using a fast Will-o-Wisp to cover for its physical bulk and spread a useful status condition, followed by Hex to have an effective 130 BP Ghost-type move, which is the strongest Ghost ever gets.)
I'm not sure if I have a
complete picture, because I don't play the tier myself, but this is what I've gleaned from following the relevant threads. Hopefully it helps a bit to understand where Dragapult stands!