His game ideas can be summarized thusly: DOOM.
The best id game, the original Quake, had both John Romero and American McGee as designers, among others, AND Trent Reznor on sound effects.
Without them, id did... DOOM 3.
What Carmack is really referring to is the gruntwork of things like writing multiple rendering pipelines to support the nightmare hodgepodge of consumer 3D hardware, trying out WELL-KNOWN rendering techniques (invented for film) in games as hardware improves, and so forth, which sometimes is just tedium and sometimes requires hackery like fast stencil shadows/sqrt/bit-twiddling tricks. Trying a bunch of methods to see what works on limited hardware is a process of discovery.
You cannot brute-force creative ideas in general in that manner.