First Person Shooter boss fights seem more limited in nature than other action games. In a game where you directly attack everything with projectiles and dodge other melee/hitscan/projectile attacks, that's not a whole lot you can do unless you expand the player moveset like Metroid Prime. The original Doom and Doom 2 kinda set the standard for many FPS bosses to come. You got your Cyberdemon, who's fast, soaks up a lot o damage, and has a projectile attack with a huge hitbox and does huge damage. Circle strafe with your biggest baddest guns until its dead! Then there's the Spider-Mastermind, which is the same thing, except he has hitscan attacks so you really have to stay out of its line of sight. Then there's the Icon of Sin, which is a unique gimmick boss that tests your endurance against waves of enemies, managing your health/ammo resources/power-ups until you can get him down from the specific height you have to kill him from. The vast majority of FPS bosses are basically one of these three variations.
Doom '16 are all essentially the Cyberdemon(including, ya know, the ACTUAL Cyberdemon) but the variety of enemy attack patterns and the use of your jumping/crouching abilites makes them rather strong tests of skill with the required amount of spectacle.
The Cyberdemon here is essentially strafing it util its dead, but he has a wider range of attacks than just the one from 1993. There are bull rushes, there are homing lasers that track your strafe, there are missles that ran from the sky that require some enviromental awareness. And then the secod form starts to introduce the walled-off attacks which require some actual jumping/crocuhing, which sounds simple but its uncharted territory for FPS boss design.
The Hell Guards are my favorite. How do you mix up the circle strafing boss fight? By making him only avaialble to attacks at certain points. This boss not only requires quick pattern reconition, but also accurate shots to attack during his brief openings. He's got a LOT of attacks, too, ranging from straight up projectiles, melee rushes, AOE stomps, and some bullet hell dodging even. And just when you think its done, two more show up, dropping the shield gimmick, but introducing even more attackswith twice as much shit to avoid.
The last one is the Spider-Mastermind, and since hitscan doesnt really work in the context of this game, he's more in the Cyperdemon mode. But again, he's got a wide range of attacks that take advantage of what you've fought up until now. He's got the dodgable projectiles, but also the deadly lasers(the closet thing this game has to hitscan). He has long range melee attacks, and aoe grenades. He's got a unique set of area denial phases that require navigating to the top of platforms, and then they flip it on you by making you get off those platforms in the middle of that attack pattern.
All three bosses have a real solid chunk of health and no checkpoints during any of their phases, so you can't just stumble your way through them phase by phase. You just have to git gud and not fuck up. 3 or 4 hits on UV can send you right back to the beginning of the fight. They all end with satisfactory QTEs, and have a fair compromise on the BFG usage, stunning the boss with direct hits leading to bigger damage and health/ammo pick-ups.
I think they're really well done, in the context of its FPS mold