It might be somewhat controversial of a take, but to me an awesome-performing Proton version of a game is far better than a Linux version that may be native, but has severe deficiencies and/or lags behind its Windows version.
To me, my favorite native Linux games would be ones that do things on Linux that are not possible on other platforms. Generally, this would be an "unfair" advantage, as games should strive for feature parity on all platforms within reason, but so often we end up being on the wrong side of that equation that seeing some of the perks of the platform is nice.
To my knowledge, the only major game I can think of that does this to a certain extent is Factorio, which enables non-blocking game saves on Linux and macOS and not Windows. It's not a Linux-exclusive feature, but it's nice that the developers went through the effort to implement the feature on Linux even though it's not possible on Windows.
It's unfortunate, but it's understandable if effort needs to be focused on a single good UI widget ecosystem fully under Mozilla's control, rather than living by the whims of the three major desktop UI toolkits they have to support, as well as the hundreds of thousands of web pages that are exclusively designed and tested against Chrome which already has been using non-native widgets across desktop platforms for a very long time. I'm not in the web dev space anymore, but I'd constantly see sites built that were incredibly dependent on the exact pixel sizes of widgets as they would render in Chrome, and would visually fall apart on Firefox, or with other zoom/text size settings.
UI design across Windows, macOS, and Linux GNOME/KDE have converged enough that it's probably good-enough if Firefox continues down the path of just theming their own widgets with the OS/user's color scheme where applicable, and calling it a day.