DRM and anticheat has been like the lead cause of all problems, even on the targeted platform of Windows itself. There’s plenty of the older games I have from younger years that were a task just to get working on Windows again, such as with ‘Safedisk’ DRM with Sim Theme Park, where you can’t even get past the first loading screen, without several patches or third-party edits just to get it launchable, in Windows.
I agree that Wine/Proton shouldn’t be the end-all solution, meanwhile as Proton came about, it seems like developers just stopped bothering to care about native builds, and too much of the community has grown complacent with Proton. But there’s also the flipside that: ironically older Windows APIs are long-term supported (also just because it’s a clearly distinguished target; a la Win7 or something), and thus it just ends up being ‘easier’ supporting something Windows-only, unless you practically ship a Docker-ish container of userspace libraries your game needs to run on, which Steam on Linux honestly somewhat is: each of the Steam Linux Runtimes (scout, soldier, sniper, etc) are just specific version-froze distro userspace libs, which a developer can target and have assurance is going to be long-term supported.
Compare with plenty of the early Humble Indie Bundle games with DRM-free Linux native builds, where plenty of them are incredibly difficult to natively install now (including having to pull in all the 32-bit libraries, and more), or not at all (because of dependency issues on a no-longer provided version of a library). Thus Linux gaming is primarily down to Valve; there could just be similar community efforts of having an alike container environment (of the same distro targets as the Steam Linux Runtimes) perhaps, to just become the norm for shipping games on Linux, otherwise I don’t know what else there is for options. Flatpak already can do some/all of that, there’s just no specific options decreed as ‘the standard options’, otherwise you’ll end up with probably like 13 different Linux userspace environments installed for like 20 games or something.