For that time period Ultima Underworld was developed at the same time as Wolf3d and had a more feature packed if less performant renderer so not long is the ans

For that time period Ultima Underworld was developed at the same time as Wolf3d and had a more feature packed if less performant renderer so not long is the answer. Then System Shock only came out a year or so later! Carmack definitely deserves all the praise he gets but there were a lot of other people pushing the technical boundaries in all sorts of ways.