For many years now KDE has focused on polish, bug fixing and "nice-to-have" improvements rather than major redesigns, and it paid off.
It has. I believe this is a consequence of the 4.x debacle 18 years ago. KDE was doing great in the 3.x release, capturing a lot of users, and then everything went sideways with 4.x.
They recovered: by the later releases of 4.x most of the problems were fixed and 4.x was entirely livable. The KDE developers learned a hard lesson and have been very conservative since then. Since the release of Plasma (5.x) in 2014, KDE hasn't self-inflicted any great regressions or misfeatures, and now there is 10+ years of "polish."
It is very nice.
I too have used the "Window Rules" mentioned in the blog post. Very useful for game development where you want certain windows to appear at precise locations on different displays every time, day after day, for years. KDE just gives you features like this, whereas this is considered unnecessary elsewhere.