There's skills and then there's basic game mechanics.

Assassin's Creed Valhalla didn't introduce the series signature Leap of Faith until early in the second act, which understandably pissed off longtime fans who had been using it as a fundamental part of playing from during or just after the tutorial in previous AC games going back DECADES.

Now imagine a similarly crucial gameplay mechanic in Harry Potter (let's say a spell that demeans a marginalized group more thoroughly than you can otherwise do), but it isn't introduced until well into the THIRD act.

THAT'S heinous game design.