I'm extremely disappointed with Space Marine 2.
No spoilers here, just mechanics and game design.

There's more focus on melee than the previous game, but without a good melee system.
All you have are 5 combos and a parry.
Ranged weapons were clearly nerfed to focus on melee.
Parrying + pistol counter does way more damage than a rifle headshot, and that's just silly.
The difference between levels of damage is small, and you're usually at close range so accuracy is downplayed as well, making it hard to tell the difference between some of the weapons since the trade offs of damage vs accuracy and rate of fire make little difference.

Tiny enemies pouncing on you can halt your advance.
For context: you are a 1.5 ton space marine.
For some reason, some wallaby sized space cockroach is enough to stop you.
The marines have very little poise in general, sent reeling by attacks from the smallest opponents, it's a bit irritating at times.

There are lots of umbrella missions, defends this, save that.
That I really hate, and it's seriously ruining my enjoyment of the game.

There's quick time events to escape grapples from some baddies, and I do so love mashing my keyboard like it's a rhythm game. \s
Fuck this shit.

Technical issues:
Some key mappings DON'T WORK, what kind of amateur shit is this?!
I tried to map grenade to '3', and it just wouldn't work, despite the tool tips showing the key, so the UI is updated correctly, and what's worse, '1' and '2' do work, and are the default keys for switching weapons.

Then there's fucked up snapping.
I'm trying to shoot the bad guys attacking a thing I need to protect, but I just countered someone off to the side, so instead of shooting, I'm snapped to the side, and do the gun counter thing instead of attacking where I was aiming at.
Almost failed a mission because of this console peasant bullshit.

The visuals showing that a counter can be made, or an attack cannot be dodged are absolute trash.
It's distracting more than anything, since all attacks can be parried except the red ones, so just show me the red ones.
Half my screen is covered in a blue circle, I reflexively press parry, NOTHING FUCKCING HAPPENS!
Because the parry system looks like the one in the Batman Arkham series, and SOMETIMES it DOES snap you to the opponent to crush their face in, but most of the time it works like in any Souls-Like, parry just before the attack hits, rely on visual cues not the blue circles, they're completely off more often than not.

You might think: "that's just how the systems work in this game", but you'd be wrong.
When the option to execute an opponent presents itself, you snap to them from a quite the distance, exiting out of any animation, and taking no damage for the duration.

Indicators that show the direction you're being attacked from are just red streaks that get lost in the rest of the screen effects when hit, making it hard to tell which direction you're being shot from.
The game is just... visually messy.
I can't quite put all of it into words, but the visuals aren't clear, and I often find myself lost.
It's not always clear enemies are taking damage, it's not clear when they die, or if attacking matters at all (can't say more without spoilers).

Then there's the FOV, the character takes more of your screen than it should.
There is no option to adjust this.