Yeah fuck this game. Way too hard for me. Im toward the end of the cultist base and I just can not beat it. Probably like 10 tries now on this one part. This shit is not fun I don't know how people like this. I thought doom 2016 was great, played it multiple times. Doom Eternal is way too fucking hard it feels like some *oooooh look bow hard I am!* Dark souls type shit. This shit sucks.
I'm going to assume you're playing it on the same difficulty as you did with the last game. At this point, I wouldn't bother: If even Civie11 - a youtuber who eats games like OG Shadow Warrior and Final Doom for breakfast - had to move the difficulty down because he was getting his ass kicked too much for it to be enjoyable, you shouldn't be ashamed about doing so as well. And then you'll have the fun you're been waiting for, trust me.
Like seriously, I fucking suck at video games, but I'm having a blast wrecking demons on I'm Too Young to Die, and easily beat the three Doom Hunters at the end of the cultist base. Game feels very much like DOOM 2016 did on Hurt Me Plenty, apart from the fact that the early levels feel like late game levels, with how many enemy types they introduce so quickly. Maybe I'll change my mind about this once I hit those damn Marauders people keep talking about, but for now, it's perfectly manageable.
Edit: oh, since I'm late, I'm gonna give you one piece of advice that might help you with the keyboard issue. If you've been constantly hitting R cause of muscle memory related to reloading in other shooters, and wasting your flame belch like so many people have, swap it with E or F. Worst case, you'll waste the blood punch, which isn't that essential on the easier difficulties, or switch your weapon mod. Not wasting my flame belch like I was early on has made the game so much more manageable. And eventually your muscle memory will stop getting in the way.