99 reasons why Hidden is dumb.

1. Chekhov's doll.
2. Chekhov's water pump.
3. When it's critical to be quiet, try not to scream. Over and over.
4. When it's critical not be seen above ground. Don't just stand above ground to slowly figure out that it's critical not to be seen, just so you can have that trailer moment where a camera pushes into the actor's face after they come to the realisation that they should get back into the bunker. The Duffers already established that they were very aware above ground was unsafe.

The rat and the tins.

5. Rats cannot smell the contents of tins. If 1 is pierced, fair enough, but 12?
4. When 1 rat eats 12 cans of your precious tinned food over a period of time, you don't notice, even if there are big gaping holes in them.
6. Rats conveniently cover up their dastardly deed of biting holes in the tins by being very quiet while doing it. 12 times.
7. Rats in this dimensionverse are so smart, they peel back a circle of label, before biting through a tin of food, then they place the label back, so the humans wouldn't cotton on until it's too late. Movie said so.
8. Rats are so sneaky they knock tins over without the paranoid humans hearing it within the small space they occupy, and not a single tin rolls on the floor. They then stand each tin back up, turn them, so the hole is hidden, and push them to the back of the cabinet 12 times. Humans also fail to pick up an empty tin until plot says so.
9. People in this film cannot judge weight. When picking up a tin of food, humans do not realise it's empty, or that there's a big hole in the middle, until the human takes the time to fully open it by hand with a tin opener. Only then, human looks inside to find the tin empty with a gaping hole sneakily covered by a label for a "waaah!" moment. Those pesky plot rats.
10. The sneaky rat even bites through the flat bottom of one tin, removes the entire contents, then places the tin back with the hole facing down, so you can't see it. Very, very smart rat.
11. After you think there are rats eating your food, you take no steps to fix the problem, until you catch them red-handed! It was a red herring anyway, misdirection, a diversion. Plot says so.......

The hatch and the air shaft

13. One minute, the airshaft is super small. The next, a 1.66m woman can fit through it easily.
14. Focus all the energies on securing the hatch. Don't bother about the airshaft. Leave the wood above it wonky, leave the vent hanging off, even if you think rats are coming through it.
15. You must whisper under the hatch. The airshaft is A-OK, you can have full conversations under it, even though it's gaping open and somehow a shorter distance to the surface.

16. The hatch door has a ladder which is shown to be 2 or more Alexander Skarsgård's high, and there are steps up from the main room to the hatch corridor. In the main room, the air shaft is an arm length from the outside, although you have to stand on a table. The ground is completely flat outside from hatch to air shaft (as shown, it's in front of the school). Makes perfect sense!
17. The bunker is quite small. The hatch and airshaft are no more than 10 to 20 metres apart. Depending on what the plot tells us, the airshaft is a great distance from the hatch. As shown by the girl running, and running to the airshaft after leaving the hatch.
18. There are no walls between the hatch and airshaft above ground (as shown, it's outside the small school). Until the plot says so, then the little girl has to pass by walls, she cannot see her parents, nor can the parents hear her screams while she's above ground.

The fire

19. "Burned wood makes ash", well thanks for pointing that out Duffer Brothers!
20. "We cover the ash". When above ground is an ash filled, scorched earth. Ash from a table being on fire underground will make no difference. Ash on ash is still ash. The Duffers needed a catalyst to push the characters above ground, and here it is.
21. After a fire 10 minutes ago, inside the bomb shelter is completely free of smoke, with no smoke escaping from the air hole which was directly above the fire, somehow a mushroom of smoke is billowing into the air from the hatch door, along with red sparkles in the air.
22. How much ash can a table fire underground make above ground. A lot apparently, it took them ages to "cover the ash".

Covering the ash, and above ground.

24. When covering a lot of magical ash, moving bits of wood around is the most logical answer. Don't bother kicking it into the other ash.
25. Someone walking above the bunker vibrates the roof, with dust and soil dropping. Bombs are fine though.
26. When shouting through the open airshaft at a high pitched scream, you cannot be heard, conveniently.
27. When a dolls voice box gets triggered you can clearly hear it through the metal hatch door, which is far higher.