Limited value and use of SuperMemo
SuperMemo teaches memorization and not advanced applications of concepts. It is useful in foreign languages, history, social studies, etc. but would have limited success for developing writing abilities or mathematics. It could work great for distinguishing grammatical errors (i.e. proper usage of it's/its, your/you're, etc.) or for memorizing multiplication tables, but it won't help you write a coherent essay or work through an algebra problem.
Placing memorization in opposition to "advanced concepts", "essay writing", or "solving equations" shows a lack of appreciation for the role of memory in all forms of human creative effort.
In all forms of problem solving, we operate with little building blocks of knowledge stored in long-term memory to form new associations in working memory to come up with the ultimate set of derivation steps leading to a solution. SuperMemo play a role mostly in that first step and helps one retain essential knowledge for years or lifetime. Some more advanced techniques, e.g. neural creativity, can also be used in employing working memory in problem solving.
For example, to write an essay, you need to start with building the essential knowledge. You will start with vocabulary, grammar, idioms and proverbs, etc. Those can be used to boost your writing skill for lifetime, and SuperMemo is great at that step. You can then start building long-term knowledge in the subject area you will write about. If you are to write about the conflict in the Middle East, you will need lots of learning in the history of the region, politics, key people, culture, etc. While exploring those, you will need to brush up your knowledge of world history, social sciences, military technology, and more. Here is the place for studying "advanced concepts", which you can tackle with incremental reading. The list of subjects to study is endless. Against SuperMemo is indispensable, and the only spaced repetition application for the job. Finally, when it comes to actual writing, you can prop yourself with tools like incremental writing in SuperMemo to compile your own ideas and citations from various sources. In the end, you can juggle up most of the work in SuperMemo, which can work as your best memory assistant. The original thought will naturally always be yours, but this is not a thing you usually bring home from school. Your thoughts and ideas will develop through lifelong learning, and your essay writing skills will keep developing over years of writing.