I agree with the general sentiment, though KDE’s apps do have some real performance issues.
Dolphin sometimes takes 2-5 seconds to open on my gaming PC, whereas Nautilus (Gnome Files) is usually done before I’ve even let go of the click.
Maybe that’s just preloading, but it makes a bloody enormous difference in everyday usage.
I prefer Plasma overall, though.
I just checked, it boots in .5 seconds on my Steam Deck. So yeah, there’s a problem somewhere 😅