Not to denigrate remix culture (which is awesome), but on a fundamental level, the re-use of IP in this manner deprives us of new IP.
In other words, the reason there is a Zelda to begin with (and this is before getting into licensing issues) is because someone created something new instead of just saying, "Eh, let's just license some other property."
D&D not only has a ton of property to explore, it can still create new stuff. That's not to say that we won't see the occasional "Rick & Morty" one-off, but the short-term boost you get from using recognized names ("Look, they have a Dua Lipa edition Adventure Path! Now that's some future nostaliga!") sacrifices the long-term integrity and growth of the brand.
For my money, part of the core brand identity of D&D is a lack of brand integrity.