I think most of the people playing the games he worked on just didn't appreciate the technical prowess and innovation needed to produce games looking like nothing before.
At the time I certainly didn't. I was constantly trying to get further and further through Head over Heels, ignorance of how hard the game must've been to write and instead my focus was on how hard I found it to play.
These days it'd be tagged 'pixel art' and 'roguelike'. Back then it was just fun, and difficult, and ultimately discarded because you had to keep replaying the same bits of the game every time you failed. I failed a lot.
It's scary to think that a lot of people entering the industry these days don't know who Carmack is, or why he's special, let alone the trailblazers that preceded him like Bernie Drummond.