I absolutely do want mechanical homogenization. Interesting variants can be handled with flavor without forcing everyone to learn completely new rules for every ability. The existence of generic rule systems (e.g. Savage Worlds) proves I am not alone with that view.
Abilities that are too powerful for that should either not exist or require significant preparation
Most abilities should be either “per round/turn” or “per encounter”.
Abilities that are too powerful for that should either not exist or require significant preparation (enough for the opposition to have a chance to discover and interrupt it).
Abilities that fall in the second category should automatically come with a less powerful variant in the first category.
Maybe as a middle ground some player abilities could use the “roll for recharge” mechanic from powerful monster abilities.
It was my impression that we are at this point discussing (rp)game design in general, not specifically D&D. If your context was D&D specifically, that explains a lot of the disagreement between us.