There's an infamous quote from "Halo" designer Jaime Griesemer where he talks about what makes the beloved "Halo" first-person shooter series so great.
"In 'Halo 1,' there was maybe 30 seconds of fun that happened over and over and over and over again," Griesemer said. "And so, if you can get 30 seconds of fun, you can pretty much stretch that out to be an entire game."
It wasn't about repeating the same fun over and over, but about creating a type of fun that could be replicated in different scenarios.
It was about "taking that 30 seconds of fun and playing it in different environments, with different weapons, different vehicles, against different enemies, against different combinations of enemies, sometimes against enemies that are fighting each other. No 30 second stretch of 'Halo' is ever repeated; the missions are constantly changing the context on you."
This ethos powers "DOOM Eternal." The moving parts in both series are roughly the same: You play as a supersoldier tasked with world-scale tasks, like taking on an invading legion of demons from Hell all by yourself, and the only way to win is by outgunning and outrunning the bad guys.
Both franchises combine superhuman movement with a small armory of weapons and gadgets, and both feature a variety of specific enemy types with specific weaknesses.
Most crucially of all, both "Halo" and "DOOM" provide the structure for "30 seconds of fun" and then iterate on that structure for hours.