Maybe you just need to read some fantasy books before you write your own - The Chronicles of Thomas Covenant by Stephen R. Donaldson, Fairy Tale by Stephen King, Glory Road by Robert Heinlein - or any of the many other stories where someone from the "real world" embarks on a 'Hero's Journey' type quest into another world, and must first learn 'the ropes'.
For either the gameplay or the written story narrative to be interesting to a player or reader, it must be about how the protagonist reacts and learns and overcomes difficulties, rather than being about the other world or the "incredibly vast hard magic system". It needs to be character driven. However, that character need not be a superhero or have any powers or ability themselves. It works better if they are just a normal 'Joe'; or a "novice". Ask yourself, how would I feel, react and overcome difficulties.
If you get more involved in this forum, then there are writing challenges and a vast amount of good advice about becoming a better writer. The fact that you know you would need to improve is good, rather than believing anyone can write and that you are already wonderful. You could begin by writing short stories set in your world.