Which of these features do you actually use and why wouldn’t you want the devs to make more money so they can produce more games that you, as a user, can play?

In case the question wasn’t targeted at them specifically: Play games on Linux and making sure the actual monopoly of Windows gets broken. Parts of Valve’s revenue goes into open source development, meaning that in the end more developers get paid: https://www.phoronix.com/news/Valve-Upstream-Everything-OSS

If game developers think the cut is too high, I’d be thrilled to see them distribute their games directly through Flathub: https://docs.flathub.org/docs/for-app-authors/submission/