>>41820906Z-Moves were never balanced, they were just less bad than Megas/Dynas. However, considering the context of Z-Moves existing only in games where Megas also existed and you could use both on your team with no downside, Z-Moves only made the games even more unbalanced than they already were in Gen 6.
Best thing Gamefreak could do is remove all of the Gens 6-8 gimmicks and just give us the alternate forms of the Pokémon as, well, alternate forms (or evolutions for some).
