I think the best example is... Epic Store itself. It is full of overpaid-for exclusives and has a huge feature disparity with Steam

Steam is older, so it's had time to grow the feature set that it needs, but it's not fundamentally different. Valve Software was a company that released games, before branching out into the much more profitable business of intermediating.

I'd argue that Epic has the opportunity see what features are out there, what is possible and what users want and could imitate Steam much quicker than it would've taken Steam to build the functionality originally.

Afterall, it was released in 2018.