It's not just the OS itself, where some of the slowness can at least be explained by the silo-ed nature of development and the large amount of moving parts. But even when MS gives a small-ish team free reign and a fresh start, the software is just agonizingly slow and buggy.

An example: new PowerToys https://github.com/microsoft/PowerToys/

The FancyZones "window snap" UI takes upwards of half a second to activate when dragging a window and the Zone Editor is at around 5s. All in all it is only very slightly less buggy than 3rd party tiling WMs like komorebic.

The PowerToysRun utility input is extremely variable, takes between 1 and 20(!) seconds. A lot of the plugins shipped with it simply don't work or have no suggestions/hints once you enter their prefix. The search relies on WindowsSearch, which is about 500x slower than https://github.com/sharkdp/fd and has not improved since Win7. Who cares, nobody ever searches for files, right? As a whole, PTRun is simply worse than https://github.com/Flow-Launcher/Flow.Launcher which uses the same UI kit as far as I can see. WTF?