I just spun up a linux Desktop machine for the first time in almost a decade and agree that Plasma has come a long way but it's still rough around the edges and, well, slow. Not as slow as the Windows UI, but still slower than xfce or the like.
One problem I do have with Plasma (though this may just be how arch packages it) - Dolphin, the native plasma file manager, is not included by default. Yes, I know it's not much of an imposition to do pacman -Sy dolphin but a file manager seems like an integral part of the system to me worthy of being included in the base package for a desktop environment.
Little choices like that affect new user adoption.
One problem I do have with Plasma (though this may just be how arch packages it) - Dolphin, the native plasma file manager, is not included by default. Yes, I know it's not much of an imposition to do pacman -Sy dolphin but a file manager seems like an integral part of the system to me worthy of being included in the base package for a desktop environment.
Little choices like that affect new user adoption.