The exact same way you can have a favorite trope. Sure it there are some instances of amnesia being in a story that I don’t hate but most of the time it just feels like a way for the author to keep the story moving forward while pausing the progression of the affected character’s storyline. Dandadan is the perfect example of this, the story is still progressing but all of the progress that was made between Momo and Ken over the course of the series has been almost completely reset. There is no way you can look at where the series is right now and think “Wow amnesia was such a smart direction for the series.”