Yea mouse was a quantum leap forward. I was keyboard only like rimmers dad there but fortunately was able to learn the mouse also early enough.
Sounds elementary but it really was keys only on almost any game but flightsims maybe, doom didnt take mouse control Im pretty sure.
The first doom was 3D but sort of hacked in, there was only one level you could aim at. If a monster was higher up, it auto aimed up. There was no need for fancy aiming just point yourself in the right direction and fire
I still only ever used the arrows for about 5 minutes, that really is nethanderal man style
how I imagine what you look like :