Shows shouldn't last for decades, no matter how good they are. JMO of course. If guests truly want the same old show from two decades ago, what do I know? At least update them so they look just as good as they once did. They're lame now by many standards. Mermaid is a shell of what it once was. Beauty has been cut and the sets are dated and so are the costumes. All of these things would have been "easy upgrades" to keep the shows fresh. If WDW wants something to stick around for decades, update the tech, update the look of the show. I'd have no issues with Mermaid or Beauty if they had been kept up to standard. Same for Fantasmic!
But I guess I'm in the minority on shows. I understand they're loved. The problem is they've lasted so long that now guests, like you, expect and want them to be there. That's actually a problem with shows. Again, IMO.
I don't look at shows the same way as I look at 'classic' attractions. I hated seeing Aladdin in DCA go, if that stuck around forever I'd not complain, because they'd likely have upgraded it. But I appreciate them trying something new with Frozen.
I just watched a video of Hallowishes from this year last night. It's still nice. I'd like to see it again. But I also want something new.
My only issue with Indy is the director aspect. I'd like a new stunt show but I love the one that's there. So I'm more torn on this one. But I'd also like an actual attraction. No reason they can't have both