I'm also impressed by Inkscape, logseq, kicad, vscode. Gnome isn't exactly my cup of tea but it is pretty polished & my parents use it fine. Psi messenger works nice. Matrix/Element is fine.

I personally think there's an unbelievably huge amount of very good nicely polished open source apps out there. Ther would be even more apps and more polish if more folks would try venturing off the Windows & MacOS paths too.