[Intro]
Helldivers 2 is an amazing 4-player co-op game (with the possibility to solo or play with randoms).
It is action based with some realistic mechanics sprinkled in (ragdoll-fall damage , ammo/mag management etc.)
It is *not* a walk in the park, especially at higher difficulties.

The game is basically a gigantic DnD campaign (Arrowhead have employed a dedicated game master after all)
where we play as Super Earth's spear - we land on planets and clear objectives for FREEDOM and PROSPERITY! (The will of Super Earth). There are various quests we - the community - get to progress the story and can get new equipment unlocked or, if we fail, even get punished with game-wide debuffs etc. There isnt a linear story like most games so you cant exactly 'finish' the game.

[Performance]
Performance-wise it runs great on older mid-tier gaming desktops thanks to built-in resolution (down)scaling , assuming you are playing at a reasonable resolution (Basically 1080p).
I have tested the game on the following two desktops:

My home PC - 80-100 FPS @ 3440x1440 - Ultra Settings (Native resolution scaling)
i9 13900k
RTX 3090
64GBDDR5 RAM

2nd PC - 60-70 FPS @ 1920x1080 - Medium Settings (Quality resolution scaling)
Ryzen 5 5700G
GTX 1660 Super
32GB DDR4 RAM

[Outro]
I would absolutely recommend the game to anyone with a friend group or willing to play with randoms.
If you want to mostly play solo your progression is going to be limited (unless you're just amazing at the game or use some solo farm cheese tactic) but honestly I'm still having fun.

[NOTE - Negative reviews & Sony fumbling the bag.]
Depending on when you may be looking at this, the game will have a lot of negative reviews.
That is due to the fact that Sony made having a PSN account mandatory, which essentially locked a bunch of countries out of the game, including people that already bought and have been playing the game for months.
Sony has had a ton of security breaches - data leaks etc so even people in PSN -enabled countries rather not take the risk.
This resulted in a huge community backlash and review bombing, which has ended (as of 2024-05-06) with Sony reversing the decision and the community is slowly coming back and updating their reviews.