I think at this point native linux ports are somewhat a thing of the past. The problem was that the ports were usually contracted out to a 3rd party and rarely updated or cared for that much. There was also the issue that they often relied on dynamically linked libraries provided by the distro rather than static linked libraries bundled with the game. So stuff that did work would break on distro updates.

The proton model has the benefit that bugs on linux can be fixed by Valve and the Wine community. While bugs in an official linux port can only be fixed by the game publisher which rarely happened. There also seems to be virtually no downsides to running a Windows game in Proton. These days I don't even bother checking the Wine DB or proton rating because unless the game is deliberately blocking linux via anti cheat, it will just work.