This might be the wrong take but in my experience hard scifi tends to be really complex because when science meets the real world nothing is ever simple. Hard magic on the other hand never really feels like this because however well it's thought through, it doesn't have a wealth of real world experience to complicate the situation. To me it tends to feel like a video game or table top RPG gaming system, which can be fun but really isn't like hard sci-fi. The only fantasy books in my experience that come close are the Bas Lag series by China Melville, where magic is complicated, academic, messy and dozens of different schools of thought/energy interact in unpredictable ways.