mine is that magic systems that try and be all realistic and grounded instead of just letting you cast fireballs and stuff suck
put a little sci fi in there. give your setting a few alien robots and laser guns.
If you look at ancient fantasy games (ADnD, Ultima), they include literal sci-fi stuff, like crashed alien ships, and no harm is done.
Who cared about alium robits, we have trolls and magic on our side


