I have Kubuntu on my personal PC and it feels klunky to me. So I am not sure why is that, since it uses the same base.
In my (admitted probably slightly dated) experience KDE kinda is like that. It’s super loaded with bells and whistles, but then because it has so many bells and whistles it’s really clear when something doesn’t work right. Personally I really like XFCE for having a decent amount of customization while being very stable and very resource light, but it does look like development has become very slow on XFCE (and afaik it doesn’t yet have any Wayland support which might be a nail in the coffin moving forwards) but cinnamon is also very nice for similar reasons