Yeah, KDE store is completely useless, one should add it to one’s hosts file and block the entire domain. 
Really, it is not fit to exist. Just like the KDE community forum. And Discover.
Ideally, KDE should implement something radically different, a store where themes are vetted and can be filtered by Plasma version. But I don’t think they have the competency or the resources to pull off something like that.
You can find a lot of Plasmoids and themes on the AUR, that’s usually a better place to install these from. Personally, I like to keep things fairly minimal, there is already more than enough blo features in Plasma.