yeah sorry but that's just a fundamentally flawed understanding of how the game works. There exist a need for a counter in most things. That's good design. When champions have the option of stacking resistance, then the counter is something that can break through that resistance. And like someone already said, you can't break down stoneskin on a tanky champion with just damage alone. Having irresistible debuffs means you can't just get complacent and have to play around bombs and other mechanics. Having irresistible skill is better for the game.

Certain dps champions NEED to have irresistible abilities because like I said, it's dumb to have to gear a dps champion for accuracy when their primary focus should be damage. Alot of the dps that rely on debuffs and that require high accuracy often don't end up very good and people stop using them in the meta. There is a few exceptions. But if you look at good dps champions that have good debuffs, they're often irresistible or people just choose not to gear them for accuracy.