if you read them you’ll see that they do blend well
it sounds like you won’t, but I have read everything published and the numerous magic systems all feel very unique, but are based on a very sound central logic
one of his foundational tenets in writing magic systems is something like exploring the limits of a magic system before you expand it, and he absolutely does that
mistborn’s second trilogy is a perfect example of that, there’s not new magic, or at least not much of it, but a remixing of what was in the first trilogy and all of the implications of that remixing was more than enough for the second trilogy











the fans aren’t insufferable as a rule, but any fanbase large enough will have a loud minority that is insufferable, and sanderson has a large fanbase
I bet had Tolkien write TLotR in 2000, well into the information age, we would see exactly the same thing
excellent world building, but plots that are fine
people really like good world building. like, really really like it.