I am aware that I could extend vim with all the missing features, but that seems error-prone and not worth the time investment, since other editors have them out-of-the-box.

Nowadays I have almost the opposite feeling of it not being worth my time and being error-prone to take up with some editor gui when my terminal already gives me an editor that does everything I want from it and in exactly the way I want it.

But I remember having your stand point when I first started to try to get into vim and getting to where I am now definitely took a lot of invested time. Wether the advantages of vim are worth your time you have to decide for yourself and it seems like you did that already.