TBH I could certainly be wrong about that. I remember playing with two hands on the keyboard and a gravis on the floor that I used my feet on to press buttons because movement was so complicated.

Yes. Very difficult to play with a mouse, but the pros with a mouse were amazing. I had a few friends that were mouse players.

The most popular choice of accessory was the Sidewinder 3D Pro. That was my choice of input device and I was easily a top 5% player in my teens.

I never touched one, but many people swore by the SpaceOrb 360 as the pinnacle of controllers for Descent.

Descent was closer to DOOM tech, not fully 3d but kind of a 2.5d . Quake was one of first true 3d games