- optimization is in the gutter, and the game feels very unpolished (year after the release!).
- upgrade system, really? What kind of game do you think you are, Serious Sam 4?
- there's too many cringy and badly written cutscenes, dialogues and radio banter. Who gives a shit the story and characters, just give me a gun and enemies to shoot at. Thankfully, you can skip all of the cutscenes and tone down voice volume in options menu.
- really weird weapon distribution. You can no longer find higher-tier weapons in secret caches, you can only get them when the story allows you. You get laser gun and Sam's signature cannon only like 2 hours before the end, in a 16 hrs long game. Where's the fun in that?
- weapons can only be found one time (except when the game takes your guns away for story reasons, then you can find them the second time). I missed an under-barrel grenade launcher, and had to play through entire game without it.
- annoying trash enemies like Processed, Mummies and Drones, I audibly groaned each time they appeared on screen. Encounter design in general is really weak, like two thirds of encounters are just mindless carnage with random enemies spawning with hardly any thought put into them.
- most of the maps are way too fucking huge and full of copypasted prefabs. Remember those stories of how Croteam wanted to make a military shooter set in the middle-east, but then it was cancelled so they took assets and made Serious Sam 3? At some point I got an impression that this time Croteam wanted to make a battle-royale game, but the deal fell through so they had to take their overly big maps and quickly turn them into linear set of Serious Sam arenas. I don't see any other reason for levels being so big and empty.
- there are "side-quests", but all of them are just a boring filler. Basically, Croteam made huge maps but didn't know how to utilize of all of this empty space, so they added a bunch of "side-quests" where you need to walk off the beaten path, clear some trash encounters and get a gadget as a reward.
- there are multiple vehicle section in the game, and all of them are boring and shitty. You can pilot a mech, but it has shitty handling and you are cramped in a tiny corridor. You can drive a crop harvester and "harvest" enemies, but it has a very slow speed, there aren't many enemies around to harvest, and the harvester also takes damage when bumping into even a tiniest bush.
- secret hunting is really lame, because most of the secrets can only be found through janky platforming. Jump on a crate, then on a shipping container, then on a lamp post, then one a balcony, then on a roof of a shed... only to find some shit like +50 hp syringe. And the worst thing is that the movement physics is very janky and unreliable, so you end up falling most of the time. I think I found like, two or three decent secrets? The one with a giant rocketeer, and the one where you find Croteam members playing football.