Tracking "current" desktop hardware is a quick way to get yourself another vista.
You're point about not tracking current is relevant though....or at least it is for some domains. When it comes to multimedia authoring you do expect people to running at least current systems because multimedia authoring is hardware heavy processes thus professionals will invest in the hardware to support them. Even weirder is the expectation that you'd want to be running a hardware heavy web-browser while running your hardware heavy authoring tools on those modest systems. That feels like you're making some unfair demands tbh.
As for KDE5, that runs fine on older hardware. I have a 7 year old laptop and KDE flies.
High memory usage from a browser or multimedia authoring tools is not the fault or responsibility of the desktop environment?
Edit: Or was your point more that the desktop environment should use minimal memory so that the user can have a better experience with their applications? That makes sense, except in this case Ubuntu Studio explicitly states that it’s designed for powerful machines and not ones with more limited resources
My guess is running a browser with Spotify or YouTube, some social networking tabs, and maybe google docs or office 365 word will not pose any issues.
Obviously the CPU is a bit anemic which is noticeable when you do CPU heavy stuff like watching non-h264 videos on YouTube, but otherwise it's been very smooth and functional.