I think lost Mines is bit of a trap in that regard actually, the BBEG no one seems to have seen/ heard of through mmost of it? Reading the module and making him more prominant improves the game immensely
I think that's true of most adventures, that some thoughtful foreshadowing can improve the overall experience. I don't think it means that it is hard to prep for, though. Something like Hidden Shrine of Tamoachan is easy enough to drop into without a lot of prep. Obviously time spent building up a backstory around the existence of the tomb will make the overall game more vibrant for the players, but it's completely unnecessary.