I feel you are arguing for real harm now, versus potential harm in the future.
There's no sign that being very-backward-compatible is holding Windows back that I can see.
In the other hand I have collected a set of utilities into my work-flow that are easily 20+ years old, and they all work fine.
The last major cull from Microsoft was that 16bit programs ceased to work on 64 bit platforms. Other than that I've never had an app fail.
Most of those utility supplies have long since disappeared, retired, or died. But I can still keep transferring those apps to the next machine and they keep running.
None of this impacts the quality of my current offerings. Ultimately all this costs me is some cheap disk space.