(Hated Meta Trope) Plot Holes that are not Plot Holes. There is an explanation if you bother to watch the movie

[u/KingZaneTheStrange]

"Plot Hole": Why didn't Thanos just make the universe bigger to end overpopulation!

Explanation: Thanos wants to kill half the population to end overpopulation right? If he created more resources, the universe would just become overpopulated all over again. He explains this in his villain monolog. There are parts of his plan that make no sense (he's called the Mad Titan for a reason), but this one is actually explained. His plan was also to punish people for their greed, and making more food would not be much of a punishment. He also has a savior complex which makes him double down on his plan to prove he's right

"Plot Hole": Why wasn't the Death Star's exhaust port fortified!

Explanation: It fucking WAS. They had laser cannons surrounding the port because the Empire knew it was a weak point. The imperial general saw the rebels and chose to do nothing about it. He says "I think you overestimate their chances". Luke needed help from Han Solo, the disembodied voice of Ben and the Force in order to get the torpedoes into that tiny hole. Han even says that the shot was "one in a million".

[u/gryphonlord]

I think the point was more to be a very visible sword of Damocles meant to intimidate and keep the galaxy in line more than anything. Like yeah, they could just bomb planets to dust, sure, but the fear instilled by the knowledge the Empire can wipe out your entire planet in one second from long range with the push of a button if you don't behave was the real point. Tarkin specifically uses it on Alderaan as a demonstration, rather than because they needed it gone

[u/Wind_Yer_Neck_In → u/gryphonlord]

They even say so in the movies, it's a weapon of terror. It's supposed to cow the population into submission because of it's absolute scale and destructive power. 

Similar to how colonial powers used to build massive opulent buildings in conquered countries, to project technological superiority and scare the locals into thinking they couldn't be opposed.

[u/Vyzantinist → u/Wind_Yer_Neck_In]

Fear will keep the local systems in line. Fear of this battle station.

[u/Gimetulkathmir → u/Vyzantinist]

Tarkin was very much about ruling through fear.

[u/Vyzantinist → u/Gimetulkathmir]

The Tarkin Doctrine is literally just rule by fear lol.

[u/Cent1234 → u/Vyzantinist]

Dantooine is too remote to make an effective demonstration, but don't worry.

[u/tryingisbetter → u/Wind_Yer_Neck_In]

Kinda like when jack was explaining the difference between jaffa staff weapons vs their weapons in Stargate sg1. One is a weapon of terror, the other is a weapon of war.

[u/Spaiochrome → u/gryphonlord]

I know from playing Stellaris that planet killing superweapons have a niche use in that they can be used for taking out planets (or even just cities if fired on a weak charge) that are fortified enough to resist conventional bombing or invading.

[u/Nikami → u/gryphonlord]

From the perspective of an unruly planet, regular spaceships are something you can fight. Bombardments are something you can endure with shields (like the one on Hoth). Doesn't mean you'll succeed but it's at least possible.

But what are you supposed to do against a super weapon that just pops into the system one day and deletes your planet?

[u/peppersge → u/gryphonlord]

It is best to see the Death Star as a siege weapon/threat. 

Hoth and the Outer Rim Sieges show that planetary shields are real obstacles. The Death Star was an attempt around it, but engineering isn’t magic. It isn’t reasonable to expect to make a shield buster small and cheap if even a super star destroyer could not bring down the shields at Hoth.

It is also the idea of a niche. A catapult or battering ram might be great for attacking a castle but of limited use in a battle between armies on a field.

[u/occasional_engineer → u/gryphonlord]

But why? The Death Star isn't designed to face external threats where such a power gap would seem insurmountable. The Death Star is an inward facing weapon for an empire that is effectively already conquered. The planets are already under effective imperial control. The aim is to maintain internal control, and I don't think even the maddest earth dictators have suggested nuking their own people to maintain control.

The problem with the Death Star is that it is far too powerful and overkill for internal problems at the expense of the day to day power you need to maintain the empire. Talking of hammer's and nails, what is the actual use case?

Some students organise a protest. Death Star? Some workers set up a trade union. Death Star? Some locals steal from the resident imperial garrison. Death Star? Some actual rebels refueled at your planet once. Death Star? At what point does it actually make sense to use it? It's like if the Soviet Union used nukes to put down the Prague Spring. The empire is made of thousands of planets that it actually needs. Only Tarkin and the Emperor think that WMD level terror is useful as a first resort.

The empire's problem is not that people aren't scared, they definitely are. It's that using terror alone to maintain order is not sufficient to actually keep a system of government working. You need your bureaucracy and enforcement of rules to keep your entire state going, and that is enforced by a conventional police and military force. At least that is you want to maintain the empire long term (though Palpatine is egocentric enough that I don't think he cares if it all crumbles after he is gone).

[u/Johnny_Alpha → u/gryphonlord]

Yeah it was called the Tarkin Doctrine and was absolutely meant to be a 'rule through pure fear' kind of deal. Of course some of novels retconed it to be that the Emperor was planning to fight the Yuuzhan Vong.