I don't think it's really an issue... The IPs that ARE in multiple parks are very popular IPs. Nemo is a good fit for Living Seas, and Animal Kingdom needs to showcase marine life SOMEHOW without doing another aquarium... Plus, the show is the closest thing you get to at WDW for broadway quality. Disney doesn't have many IPs to offer when it comes to marine stuff (except for Moana... It was just a little late when they rethemed the pavilion.)
Beauty and the Beast's live show is, while dated, still pretty dang popular amongst park guests, and it's not BAD. Just because a bunch of crazy Disney park-goers have seen it a billion times doesn't mean all of the once-in-a-lifetime tourists are gonna skip it. (I don't care for the show, for the record. But kids and families do love it. Check out the Annual Passholder FB pages) Sorry, we don't make up the majority. Also, Be Our Guest is a FANTAASTIC atmosphere of a sit down restaurant. The sing-along, though? I can't back that one up. Also story time with bell is a small chunk of land that was VERY well executed.
The Little Mermaid dark ride was a good addition to MK. Voyage of the Little Mermaid is probably the most dated show on property... But it's not taking up much space. And for the tiny space it DOES occupy, I'd say it's a pretty solid show. Especially for the kiddies.
Frozen has a very well-received show at DHS. Very popular amongst kids, teens, and tweens (it's trending on tiktok). And Frozen Ever After, while it replaced a classic, the classic was in terrible shape, and again, the space it occupies is really such a small chunk of EPCOT. The meet n' greet was done very well too.
Buzz Lightyear SpaceRanger Spin & Toy Story Mania are, shall I say, the "same thing," but they are also very different in their own ways, and that makes each ride its own truly special experience. Toy Story Land was alright, I don't think it needed a WHOLE LAND. But it wasn't executed terribly, tbh. It's a cool land.
So.... As long as it is executed properly, it's not a problem.