While it’s true that a good Games Master can make a good game out of just about any system, that doesn’t mean that system doesn’t matter.
There tends to, still, be a trend of people using mismatched systems. Either for economic reasons (2d20, 5e) or because of fashion/cultish reasons (PbtA). As a result there’s a lot of compromised games out there without tailored, or even properly selected, systems for their game world.
Imagine trying to run a Hong Kong action film game using Basic Roleplaying.
Imagine trying to run an existential horror game with Feng Shui.
The best games work well more often, because their system and setting are in synergy, complimenting one another.
Call of Cthulhu works best with BRP, because BRP is granular, simulationist in many respects, and yet its monsters break all the rules and there is a way of tracking sanity.
Hong Kong action movies work best with Feng Shui because Feng Shui encourages over the top descriptive action with nigh indestructible heroes.
Military SF works well with Silhouette, because it scales and can be used for skirmish-level miniatures play as well as standard tabletop RPG.
Whether you’re making up a new game or kitbashing an old one into shape, the right system can make all the difference, or at least do a lot of the heavy lifting for you.