In high school, the teacher is expected to think for you, to package everything in small digestible bits that can be memorized for multiple-choice tests. For the most part, you are trained, not educated, taught to memorize how to do something, rather than understand how to do something, or to memorize facts instead of understanding how systems work. Problem-solving is not part of that package, for sure.
High schoolers become accustomed to the thinking part of their brain being in first gear, or park, rather than in top gear. “Idle”.
Game design is all about critical thinking; one well-known “indie” video game designer says it’s 99% critical thinking, though I won’t go quite that far. The teacher cannot think for you, in game design, you have to think for yourself. And thinking is undoubtedly hard.
Too many people think they can get an idea and someone else will do the work–work which involves a great deal of thinking. Too many think they can easily make a game “just like such-and-such but better”, having no idea how hard it is to make really good games (it’s easy to make poor ones). When they’re posed the problem of making a game that isn’t “just like such-and-such”, they are floored.
Further, game design is about problem-solving. In general, a prototype game is broken. The game designer must figure out ways to fix it, and then ways to make it even better even though it works, because lots of games that work aren’t really very good. These are all problem-solving exercises.
If the initial conception is fundamentally good, then there’s a lot of work to be done to get a good (or better) game out of it. If the initial conception is poor, then it will be difficult if not impossible to get a decent game out of it, and that will require abandoning some of the original conception. Even if the initial conception is “wonderful”, there are thousands of ways to mess it up.
Yes, there are hard jobs that are nonetheless rewarding and even fun. Dave Duncan, a well-known science fiction and fantasy novelist, didn’t start publishing novels until he was laid off from Canadian oil fields at over 50 years old. After 33 novels, he said writing (which is largely thinking) was still hard work.
Sometimes, designing games is hard work because thinking is hard work.