The problem is that most YouTube videos are from enormous whales. Like, the last boss "only" has 7.5m HP. That's exactly the burst damage cap, for off-element. So whenever you see somebody oneshot the bosses, you should be thinking "uh, is that realistically possible or not...?"

For non-whales, reaching damage cap is really, really, REALLY hard. Like, using a calculator, I could be using double Kirin (which I don't have) against Water, with a full SSR team (which I don't have), with -50% Def (which I don't have without Dartagnan) and I'd be able to reach 3.7m Burst WITH Provisional Forest.

Sure, my base attack and slightly my grid would improve over the many months before AQ5 comes here, but it's really difficult to imagine going above 5m Burst...