I can’t see how native Linux support is getting worse. Linux users are good at bug reporting. Maybe some developers should care more about compatibility. And yes, especially the heterogeneous setups used by some makes support difficult.
I’m worried that Valve puts too much resources into Proton (derivate of WINE) instead of tooling for native ports. Yes, Proton is needed to provide initial compatibility. But Proton is another layer of complexity (more bugs, integration, system resources) which requires more programming. I started playing CS again after it was ported natively in 2014, it runs well and all issues with WINE were gone.
If Proton becomes to “good” we end up in a situation with a high maintenance burden for Valve. Game developers will rely on it and Valve has all the constant work. Instead game developers should treat Linux as first-class platform for AAA-Titles, for which the need appropriate APIs, compatibility and tooling. As Valve does itself support Linux as first-class platform from HL2 to CSGO. The target shall be official support from the very first day.
Anyway. Looks like Valve has chosen a special implementation for TF2? What I miss here is a link to a bug report. Ideally opened months ago :)