There was a time when Apple was pushing full screen mode as a solution to a cluttered desktop, but didn't seem to realize that full screen mode sucks on really large displays and that people are often working with one or two apps at once and don't want to have to switch back and forth all the time.
Stage manager seems to be them finally acknowledging how people work on Macs. Hell, the renewed attention Apple is paying to the Mac is a breath of fresh air. I always found iPads to be restrictive.
The only thing that I immediately noticed and am not crazy about is that you can’t use split screen view with stage manager. I frequently need to see two apps side by side.