Think of it this way, who cares if you like the actual Harry Potter stories, movies, etc.
Do you have to like "Song of the South" to enjoy splash mountain?
Do only the biggest fans of "The Mummy" remake enjoy "Revenge of the Mummy"?
Can you build an entire new land with one attraction based on a large mythological creature in a mountain, have the ride be decent but the creature disappear? Does the general public care? No, they don't.
However, even if you don't like Harry Potter it has been the greatest single success built at any theme park in the fastest amount of time ever.
If instead of "Avatar" WDW was going to build an entire "Star Wars" area there would be people that would complain and multitudes more who would be there happy to pay admission and buy merchandise just because.
Does it suck to lose JAWS? Yes. Don't let nostalgia blind you, watch "BTTF the Ride" again. It wasn't really that good of an actual ride. Did you identify with the characters and story, sure. Was the ride itself that good? Not really.
I don't ride "Revenge of the Mummy" for any other reason than it's an amazing theme park attraction, so why not get excited for more attractions from the people that built Spiderman, HP&tFJ, Revenge of the Mummy & others at or above the quality of the Wizarding World of Harry Potter?