We have characters with resource meters. It’s not that hard to design characters that have strong abilities that don’t come back by just waiting. I can just off the top of my head think of a whole lot of ways to make a high impact play button for a character that isn’t just make them wait a lot between uses.
Have it need a lot of a resource that is shared between your other abilities;
Have it need a long cast time that leaves you vulnerable and warns your opponents with a sound queue;
Have it need set up from another ability in the form of a destructible deployable or needing to land a debuff on an enemy;
Have it be refreshed on picking up health packs, it could even “spend max health” that is restored when you pick it up;
Have it disable your other abilities for some time after using it, cutting you other contributions for a bit of time after it’s used;
Anyway, game design is a very big world full of interesting and shiny things that do fun and quirky stuff but overwatch devs just keep using the same ones and honestly it’s getting boring.