There’s a trillion ones around unrealism, so I may as well pick something that would be more enjoyable if fixed.

Professional chatter. Let’s say a team of 30 scientists have been trying to communicate with a dimensional portal for 5 years. They wouldn’t be using speech like “Identity verified. Doctor Faris, you are clear to approach the anomaly.” Often, they’d have extremely abbreviated lingo for everything they need to express that happens on a daily basis, and otherwise are chatting about other stuff.

“Ok, approach endorsed. Bob wasn’t so chatty yesterday from what I heard, we’ll just aim for 2 logic points for this cycle.”
“Ryan was suggesting we spread the cycles. Bob has to sleep sometime.”
“Yeah, 90% of us would rather listen to Ryan than Mick, but Mick signs the checks.”

So the only actual order comes from some obscure phrase like “Approach endorsed”, which they may only say verbatim for safety reasons. The rest is just workplace banter about how best to accomplish their task, none of it being essential. EDIT: And, to make clear, in the above quote, Bob is the portal/anomaly.

A more mundane one, but people on reasonably normal incomes living in a house that's at least one order of magnitude more expensive than they could ever afford even if they purchased it twenty or thirty years ago. Its particularly bad in things set in expensive areas like London or New York or Tokyo. Like being able to afford a house in central London rather than renting a flat with three other people takes substantial money, you aren't going to be afford that if you work in a supermarket.

The film Under Siege II has some of the best hacking scenes and dialog.

Even at a young age, the line "This is the guy that hacked into the Pentagon with a laptop" made me WTF because unless you're brute forcing encryption, the kind of computer you use to backdoor a system is irrelevant.

The ones that really get me are the way they show execs at companies. The "look, this character is so bad ass at being an exec!". They always come off as so unrealistic and cringy.

I've swam in that ocean, and that's not how that shit works. Engineering too. In reality, it's always a team of engineers that get something done... It is NEVER some rich smart guy inventing stuff on his or her own in their super fancy workshop.

If a girl doesn’t like you, but you just keep pursuing her, everything will eventually work out and you’ll be happy together.

How night and day work above the Arctic Circle.

Movies and TV and stories talk about how there's 6 months of daylight and 6 months of darkness. That does not fucking happen. This is still part of storytelling to this day (I'm looking at you, Sweet Tooth season 3).

Days get stupidly long in the summer, and there's a while where the sun really doesn't go down. in the Winter days get stupidly short, and there's a while where it doesn't really come up all that much. But it's not 6 months of one and 6 months of the other.

(edited for clarity)

Stepping on a landmine doesn't make it explode instead it arms the mine with a noticible click sound then lifting up your foot is the thing that makes it explode.

Where in countless mystery/thriller stories bad guys arrange meets in huge open deserted buildings, to be uninterrupted. In the real world, the place will securely locked and gated, or multiple houseless people will have already moved in there.

The first time I remember absolutely losing my suspension of disbelief was at the end of the first Mission Impossible reboot where Tom Cruise puts an explosive on a helicopter he's hanging on the outside of that's flying behind a train through a tunnel, and the explosion completely destroys the helicopter and flings him onto the back of the train. Yeah, that helicopter (which probably couldn't be flying through a train tunnel to begin with) was made of far tougher material than Tom Cruise. Any explosion that destroyed it, would have turned him into a stain on the wall of the tunnel.

There's this scene at the start of War of the Worlds where the hero races his classic muscle car up this tiny neighborhood street at full tilt, exhaust notes at full blast, and I think he even screeches the tires by slamming the brakes pulling into the driveway. Then he walks up to his neighbor and they're all chill with him. In any other world, the neighbors would have him in handcuffs.

The law, in basically everything.