The other side of this seesaw is: Games are fundamentally in the novelty business. Players like some amount of familiarity, but they want new experiences. Every game engine has a sort of "grain" to it where it tends to produce games with a certain look and feel. The flat-ish shading and floaty physics of Unity is a particularly visible example of this. So using a widely used game engine can put you at a disadvantage if you're trying to make a game that doesn't go with that grain and offers players something different.
As more studios consolidate on the same engine, more players will get tired of that sameness and reward other studios more. As more studios do their own thing, players will become saturated with novelty and the benefits of not using an engine will go down. There is no stable equilibrium.