"DOOM Eternal" is not a precision-based game. If you pull the left trigger, your character doesn't pull up iron sights. There are parts of enemies that are more vulnerable to certain types of attacks, and that can be important during especially intense fights, but you don't have to worry about not being an FPS master.
Instead, "DOOM Eternal" focuses on what I like to call "The Dance."
Let me explain: At any given moment in a fight, you need either ammo, health, or armor. If you pull your chainsaw and saw an enemy in half, ammo explodes out of them. If you hurt an enemy enough that they start glowing, you can perform a one-hit "glory kill" that makes health explode out of them. If you set an enemy on fire using your shoulder-mounted flamethrower, armor pops off of them; if you kill the enemy when they're on fire, a fountain of armor explodes from the body.
At any given moment in a fight, you have to monitor which of these resources you're most in need of, and prioritize which enemies to kill and how to kill them in order to gather resources.
Some enemies are huge, and soak up a ton of bullets before going down — you may need to tackle some easier enemies to replenish ammo/health/armor before taking on that mancubus!
It's this resource management, combined with the absurdly fast movement of the main character, that makes every fight feel like an absurdly violent dance.