That Ableton upscaling is better than nothing no doubt, but since scaling isn't standardised we can see the issues.
I don't know if the graphics rendering will change in version 6, I imagine it won't add GUI upscaling but at least you will see advancements in the theming tools to accommodate scaling new themes, and with more VSTs internally scaling their GUIs this is becoming less of an issue.
Proper scaling is pretty darn useful even if you don't have a high DPI or 4/8k panel. Much easier to work on sounds having a software synth fill most of the screen.
Glad you found the theme link useful.