Better in latency and throughput without GPU-accelerated rendering while being feature-rich, that's the point.

forgive me if i don't take your word for it. I remember K-everything being slow as molasses and have avoided K-anything since.

That's wrong since like KDE 5.10. Better test first before assumptions

if it took 5 major revisions to address obvious and appalling performance problems then I'm quite sure my desire to stay away is justified.

It didn't take 5 major revisions. There was a big regression with KDE 4 compared to previous versions, and that was remedied in KDE 5.