I understand your sentiment, though as Armsty says its not true that there are no tutes on how to make stuff good. I've written a specific tute and also have included tips (relevant to the particular topic) in other things.
creating good missions macguba's guide to mission editing for beginnersBeta testing board sticky topicQuick guide to reducing lagI plead guilty to self-advertisement but you did ask. There are other things kicking around as well, if you look. However OPFPEC is a big place and it takes some doing to get round all of it.
There are many excellent missions, and plenty of good ones. Unfortunately there are many more crap ones, as you say. There are two reasons for this. Firstly, mission editing is difficult - to make your first mission takes an enormous amount of learning. Even quite decent first missions are rarely little more than functional, which is no surprise. The second reason is that making a good mission is REALLY difficult. Most people make missions primarily for their own mission making pleasure (not the pleasure of the player, that's a bonus) and actually making a good mission involves a great deal of hard work and tedium. Many mission makers, quite understandably, do not wish to put the enormous extra effort in to take a mission from ok to good.
To make a good mission takes several hundred hours work, assuming you already how to make a functional mission. If you have a job, school or college to go to you can't possibly make more than 1 good mission a year. And that's assuming you have the talent to make a good mission in the first place. Practically anybody can make a functional mission if they choose but as with any art or craft some people are better at it that others.
Why is it so difficult? Here we get to the nub of the problem because many people don't appreciate this. It's nothing to do with scripting or cutscene making skills. (Although obviously they help.) It's nothing to do with good plotting, good dialogue and good characters. (Ditto.) It's to do with the interactivity of the game: you do somthing, it has a consequence. The hard part of mission creation is setting up a situation where the player has a set of options all of which you, as the mission designer, understand. You then must create consequences which are appropriate to the player's actions.
It's impossible to do this completely (which is part of the joy of playing the game) but a good mission does it pretty well, which is why you feel satisfied after playing it. Expectations have been created and met: good behaviour has been rewarded and bad behaviour punished.
The three "high level" tips I always give are these. Firstly, remember that when making a mission you are telling a story. Think back to primary school - we need a sense of place and time; beginning, middle and end; identity with the central character; good supporting characters and so on.
Secondly, think very hard about consequences. What would the player do in reality? If you want him to do X, make the reward (or punishment) appropriate. A general example of this is a defensive position: if the player attacks it head on he should meet strong resistance. If he goes round the flank he should meet lighter resistance. Simple but effective.
Thirdly, playtest, playtest, playtest. As an example, if you want to make a good mission then you Preview the mission as every single unit in it, just to check his starting situation. Can he move off ok? Is he facing the right way? Is his weapon loadout correct?
That summarises the problem. If you want to make a good mission, you have to check every unit. Half of them will need to be changed, which means you have to check them again. Then something else in the mission will change, which means you have to check some of them again. And again. It can take 15 minutes to place a sniper even after you've decided which bush to put him in. Later on, you will probably want to change the bush. That's another 15 minutes.
If you don't test at this level, some tiny details will be not perfect. These tiny details, although not that important in themselves, multiply up to make that imperceptible difference between an ok mission and a good one.