True, but... Okay, I've been going to DL every year since I was born in the late 50's. For me, the park stopped being "Classic" Disneyland when Nature's Wonderland got removed for Big Thunder. Frontierland's always felt smaller after that. But I do love Big Thunder, too. Then Inner Space got bumped for Star Tours and Jungle Cruise got shortened for Indy, Fantasmic ruined nighttime New Orleans Square but gave us a great show, Tarzan turned a wonderful treehouse into something kinda tacky, Fort Wilderness closed, Tomorrowland got ruined, Autopia widened and got boring, DCA made sure no one would ever be able to approach DL's main gate from the front (it *still* feels weird for me to approach DL from the side). And the Country Bears, one of the most amazing AA shows ever created, got torn out for a C-ticket dark ride.
Star Wars Land will certainly change DL forever, but it's adding something huge and potentially amazing. It's a gigantic change, but not as huge as the addition of DCA and Downtown Disney. It won't be a disaster like the Tomorrowland redo... (we got NOTHING out of that except Buzz, and it wasn't worth it). Yet even with a sad, ugly Tomorrowland, DL is still an amazing, wonderful place. After Star Wars Land opens, DL will certainly feel different, but it will continue to be amazing. This is an exchange of a bit of atmosphere for an incredible new land, but Fantasmic already changed the river forever, and far, far less beneficial changes have happened in the past. I think it's going to be okay.