Half-Life was built with the Quake engine and heavily inspired by DOOM.
Although sort of true, it was 90% not Id code.
Carmack's last hit was Quake 3. That engine sold bucketloads. You think he's mattered in the near decade since? Then take a look at how many Doom 3 engine games are out there that aren't financed by Id. You can count the number on one hand. Factor in how terrible Doom 3 was, and you've got the worst selling major engine of this generation.
Not to say the guy isn't one of the best technical coders out there, but he really misplaced his efforts when he concentrated so hard on lighting beyond what most PCs could do.
Meanwhile, from what we've seen of Tech 5, it looks to continue his inability to do necessary lighting techniques like making humans not look like rubber. I hope he fixes that, as I've played one rubbery-human game too many. I'm still waiting for a game to make people look better than Half-Life 2 did so many years ago.