they perfected the game-loop, Doom has finally reach its final form .
now it has shooting, slaying, mobility, resource management, weak point system and a story (which doesn't really matter, just for hype)

the series went from:
1 & 2 Dooms - simple atmosphere and shooting in 3D environment, where it was revolutionary at that time.
Doom 3 - corridor horror jumpy kinda game.
Doom 4 (2016) - rebooting and implementing new techs, but with flaws, many directions and short.
Doom 5 (Eternal) - figured out its own direction and went full on with it, which why it's going to take some time to get used to the new system.

Edit: since this Review took off, expanding it with more info to save you TON of time.

1) To claim Bonuses, Settings > Bethesda > Reclaim
2) To change linked account, Submit ticket to Bethesda Support to Un-link.[help.bethesda.net]
3) Family Share only shares base game, no bonuses yet, but works fine.

1) low FPS, lower Shadows, Reflections, Lights and set Dynamic Resolution.
2) low health > glory kills, low armor > Fire bench, low Ammo > Chainsaw.
3) Check Settings Menu before playing, tons of options, UI colors, classic Weapons pose and sounds and more.
4) Slayer Keys disappearing, de-activate Cheat codes from Select Missions > press R.