I had an almost identical experience to the parent, though I went KDE a little earlier than the publication of that incredible article, "GNOME has no thumbnails in the file picker (and my toilets are blocked)" [0]. It's absolutely worth a read, regardless of your chosen DE.
...but after you're done reading it, perhaps you too will change your mind.
Funnily people bash gnome/gtk for the no thumbnails in file picker but nobody bashes kde/QT for no sound or video file preview either.
When I am in kde/kdenlive, sure I get picture thumbnails but I don't have thumnails for videos from my camera nor can I hear the sound files by playing when hovering over the icon.
I'd argue the file picker thing is just a standard-bearer for a whole bunch of different problems. Just look around this comment section, GNOME has more problems than thumbnails. KDE might not solve them all, but I'd argue its proverbial toilet works much better.
I am using both, I have one laptop dedicated to kde to make sure I don't miss out on anything in case both evolve in different directions. I make sure I still use the kde one once in a while...but I still tend to go by preference to the one running Gnome.
So they might have more problems but it doesn't necessarily translate in worse user experience for all users. The file picker was one example but I don't see me use very often a file picker, I am more a drag and dropper these days. It may be because file picker is not that great on Gnome, but I just checked the kde one today...and realized that meh. I'd still rather use dolphin on kde to drag and drop to a particular app than go to open --> file and choose it in the file picker. It seems just more convenient to me.
So KDE seems more flexible, and may fix issues that count for the 0.005% of the population, but the configuration panel feels like an airliner cockpit. Gnome may not care about what annoys 0.005% of user but the experience seems to be more straightforward to many and less choice means less stuff to configure to your liking the day you switch from one computer to another. You'd really have to backing up your .config preciously if you start customizing kde to your liking.
In the end it is great both exist, as well as the alternatives and the standalone window manager. On screens 10" and smaller and on older and slower machines I still prefer using a tiling wm.
Hm of course I backup my .config. After all, this is Unix and most programs have their own settings in the .config folder and many other places. This is not an issue for me.
...but after you're done reading it, perhaps you too will change your mind.
[0] https://jayfax.neocities.org/mediocrity/gnome-has-no-thumbna...