Bare-bones AI - Every bear, every scientist, every chicken have eyes covering every square inch of their heads. And those eyes have 100/100 vision, able to seeing through walls, in pitch black, through your base. Just play around with a scientist by peaking in and out of their LOS, then you'll see just how miserable PVE is in this game.
Toxic community - Bustling servers entail the loud and obnoxious, uncontrollable racism, full-time griefers, clans seeking record time in making new players leave, uninstall, and demand a refund. Sparse servers entail unfettered door campers, stalkers, ESP trolls and stash swipers/breakers.
Hackers - Hackers are EVERYWHERE. Some smart about not getting caught, some not so much. But they are EVERYWHERE, because Rust is apparently not as complicated of a game and crucial coding not so ssafeguarded. Who would've thought!
Strict but barbaric Anti-cheat system - How many fluke flyhack violations will it take to get to the tootsieroll center of a tootsie pop?
This game is nearing its 10 year anniversary and the amount of bugs and game flaws/exploits I come across is unprecedented. Mini helicopter suddenly go boom mid-flight. I'm standing on top of a tipped boat, then somehow mount it, sitting upside-down, underwater. 5 bears clipped inside a marsh shack, I get up close for a screenshot, then they all noclip out like a scene straight from the grudge. A stranded floatation despawning from right under my feet, literally LAUNCHING me 15ft deep in water because that obviously wasn't intended to happen. Safe Zones hurt you more than help you.