I know the state of app preservation on iOS is miserable, but in all fairness most of that stuff wouldn't work today anyways since most apps are just glorified websites (though there are some things like video games), but macOS is a real platform with real software. But there's just this great chasm of missing software between whenever Apple stopped distributing stuff on disc and today. You want to find some specific version of iMovie you can run on some Mac machine that's not too new but not too old? Too bad. You can either run the last disc-based version from 2011 or go buy a new Mac machine to run the latest version. It kind of sucks.
https://archive.org/details/ilife13
So I suppose once you convert an App Store package into an independent .dmg, it can no longer receive any of its iterative updates. You want that update for iMovie 10 that fixed a particular bug? Fuck you.