KDE5 isn't even out yet. We are at a transition place since they broke the project up into it's constituent parts. But KDE Plasma 5, the desktop, is great. I'm using it right now, posting from a seven year old piece of shit Dell office computer and it's snappy, responsive, and well laid out. Way better than KDE 4, I don't know how you could think otherwise. Just switch to the classic KDE menu + dynamic search box, get a new theme from KHotNewStuff, and enjoy.
I like the default settings, but judging KDE on it's defaults, like what seems to be happening a lot, is pointless. KDE is like Foobar2000, power-users like enjoy that there is some assembly required.