The problem is that the blur effect that's considered "modern" nowadays is way too strong, so strong that it might as well be a solid colour when comparing it to real Aero. It looks fine for flat themes, but looks terrible if you've applied a skeuomorphic theme, like the Longhorn -> 7 themes, or a custom one, to your desktop (which is why WindowBlinds 11's Aero themes are even worse than 10's equivalents).
On the bright side, I AM very happy about the upcoming Windows 11 titlebars being made to apply the blur to browsers' tabs in the same way that Aero did (the tabs overlapping the titlebar while the titlebar itself maintains the effect)!
