I think the problem with the '90s music is less that there's such a limited number of songs that will work and more that teams aren't getting creative enough.
It feels like everyone is choosing from the same pool of pop music: boy bands, Madonna, Spice Girls, poppy hip hop, etc. Then there's those that are doing nonsensical remixes that don't capture a particular musical moment of the '90s. All of this makes it seem like this is less about celebrating the '90s and more just going through the motions. It's as if they asked ChatGPT for '90s music people like and boom there's their RD.
There's a lot of good '90s stuff that is just being ignored and would make for much better programs that reflect interesting musical movements of the '90s: grunge, ska, punk, alt rock/NuMetal, pop rock, R&B, female rappers/country artists, etc. There's so much music you can't blame rights issues alone.
I can't wait to see Piper/Paul's RuPaul RD. Carreira/Ponomarenko's Crystal Waters RD is also great. Take us to the club. So there is creativity out there - it's just very limited.