How would you provide a "standard" environment when the third party apps all depend on other third party apps. What would the "standard" environment be for streamlink when it itself is part of the "standard" environment of streamlink-twitch-gui? How about curl, mpv, ffmpeg, libc? How do you evolve such a "standard" environment without the assistance of the third parties (because many of them will never help you).

Debian puts in a massive effort to be a long term stable "standard" system. I've found that effort to be wasteful. I'd much rather just take the occasional (although surprisingly rare) breakage than live with the limitations of old packages. That's a matter of taste though, and greatly depends on the effort of the upstream developers.