Customizing the look, feel, interaction of elements, and general mechanics, seems like a toooon of effort. (It kinda seems like you’re not supposed to customize it.)

Sometimes all of this is there for a reason. I used to really hate standard Windows (and I still do) but it had one big advantage: everything was accessible, in the sense that it all worked very well for blind and vision-impaired people. Usually when people create their own custom look and feel etc. they never accommodate accessibility at all.