What you're saying is "inevitable" hasn't happened for the entire 20+ years of Steam. I'm going to guess Valve is going to continue being a private company and doing whatever the fuck they want, without investor pressure towards enshittification.
Steam's monopoly is actually what's holding PC gaming together. Other types of digital distribution services are so fucked up by exclusivity deals that any "competition" is always going to mean "megacorporation uses existing wealth to deny competition".
Epic is trying really hard to bring the exclusivity nightmare over to PC gaming as well, but so far Valve still holds.
These plugins just never work quite as well as a browser made specifically for it, namely Qutebrowser. Trouble with Qutebrowser is that's it's Python and parsing a lot of links slows it down. Still the best browser out there for this use case though, as far as I know.