KDE still hasn't figured out that sometimes less is more. It wants to be a Windows knockoff but throws more buttons and menus in the face of users, introduces too much unforgiving behaviour, lacks discoverability, has too many settings, has little consistency between core applications and expends little effort to ever to address these issues. It's a dog's dinner of a desktop.
And when you read KDE's human interface guidelines it becomes clear why it's such a mess. The HIG reads like a developer free-for-all. It points at existing apps as precedent, or mentions some class or another, or waffles into wordy sections. But what it doesn't do is layout a clear vision of what KDE UX should be including illustrative examples, usage patterns and so forth. Some of the HIG is hilariously stupid, such as explicitly refusing concepts like basic & advanced settings. No wonder its a kitchen sink.
Compare to the GNOME HIG if you want to see what a HIG should be. And no that doesn't mean KDE needs to "dumb down" to become GNOME but it needs to lay out its stall in a way that developers can follow and its UX needs to be designed on sound principles. e.g. KDE has Kirigami to produce modern usage patterns, so write the HIG around that. Make it fit for purpose and maybe some of that kitchen sink mentality will go away.