My first thought upon seeing this was wow, a DOOM clone on PICO-8, that is some next-level technical wizardry. That in and of itself is impressive.
What I found at least as impressive as I played is how well this nails being DOOM. It's not just something vaguely resembling DOOM but a proper DOOM demake. Some of the details are off, of course, but a surprising amount of stuff is right on, and most importantly it feels right. Of particular note is the movement, which felt absolutely right, and I'd just finished playing some of the original this morning.
If I had one gripe it would be the level design, which I found kind of eh, though given the technical limitations that were no doubt involved I'm more than inclined to forgive it.