Yeah, I do miss that, but idk how much of it is nostalgia and how much is an absolute aesthetic preference. I think the main reason for the change though is Microsoft trying to make Windows work well on mobile devices though, meaning forgoing the aero and more expensive VFX.
Wish some DEs would make their default style more like a win7 era style. Would be nice to have the variety.
It is legal but in any case why do you care. If it were illegal it’s not something that would be enforceable or something they’d be likely to “catch” you for, and it’s definitely not unethical. Everyone should be free to do whatever they want with published literature.