Doom Eternal is basically set of small arenas connected into single level with some short path in between. Upon entering each arena enemies start to spawn from all angles out of thin air. They keep spawning up to certain number as you keep killing. Once cleared, you move on to the next are(n)a and so on. I will leave it up to you to decide if this is a type of fun you would expect from an overpriced video game. Because of this level design you eventually start to realize it kill any sense of mystery and imagination and AAA graphics just won't save it.
Furthermore, game intentionally limit you to ammo and losing health and armor is relatively easy. Ammo at full capacity is particularly low as you are supposed to keep refilling it through button press "gore" action - same for health and armor. So as you get short of whatever you come close to random enemy and execute one of three "gore" actions(read buttons), each in particular to refill either ammo, health or armor. This effectively kill any joy and sense of certain freedom capacity you know from any other shooters. It is supposed to add some management level and complexity but end up feeling "narrow", just like the level design.
This game should come together with Doom64, N64>PC conversion. That one is like 9/10 and pretty much as good as Doom 1,2 were. The difference between that one and new Doom Eternal is unbelievable. Level design, that drive to play, forgetting what time is it... its all there, you realize you did not get old, its the game. Doom Eternal is an ultimate garbage of lowest caliber, cheap uninspired level design, atrocious gameplay and total lack of imagination. Play Doom64 only and skip this garbage, unless you don't value your limited lifespan at all.