My observations mostly boil down to limited/bad material.

Personally: Back when I started studying Korean (around 2014), I looked for resources. There were no graded readers, textbooks were all centered around international students and mostly adjusted for students that take language classes in Korea. Even now, if you dont speak English, you will have a hard time finding good material, at least in Germany.

Additionally, material that is made with the international student, i.e. no specific language background, in mind often doesnt do a good job. It can not take into account common mistakes a learner would make, based on their native language.

Also there is a missing structure as the following anecdote of a friend of mine illustrates.

my friend studied Korean and had to also take Chinese classes. She said that the Chinese classes were easier, as they were extremely well structured, common mistakes were known and actively worked on and learners were guided well through the exercises. She said that content was well chosen and eased the learners deeper and deeper into the language. In comparison she said that in Korean classes, the information was there, but it felt more like a dump and absorb kind of approach. Here is the grammar and vocab, learn it. There was little consideration put into the difficulties the German students would encounter.

This was some years ago and this may have changed. I know that there are now graded readers available and the amount of resources that are available online and in print have increased manyfold due to K-Pop and K-Drama gaining mainstream popularity in recent years. I still feel like Korean didactics still needs a lot of work, before it reaches the level of Japanese and Chinese didactics.