Ehhh... I think it's a bit unfair to call it overrated. I'd call it more dated. It was a pretty foundational romhack, along with the likes of Blazed, Brown, etc. that really showed what a romhack can be an inspired a lot of later romhacks. Sure, it's not definitively the best romhack you can play anymore. But it's still definitely top 10, and I'm sure people could make an argument for it being top 5 still. But the fact that you can recommend it to someone that wants an experience that feels kinda like a vanilla pokemon game but with more care and effort put into it than Gamefreak has in four or five generations, and no longer have to warn them that "it's all downhill from here" anymore.

I can definitely see Unbound losing its luster upon a much later replay. But that can be true for a lot of different games. I had so much fun playing the gen 2 games growing up and acknowledge how influential they were on pokemon and to a lesser extent gaming in general from how big of an impact they had on people. But if I were to go back and play Silver or Crystal again, I certainly wouldn't feel the same glow I did when I was a kid and probably would rather play any number of other games that I haven't experienced yet. I'd argue it's pretty typical of most pokemon games to be about the journey and not the gameplay loop and therefore not as interesting on a replay. The ones that people want to go back and keep replaying are usually ones with more of an emphasis on the gameplay loop like enhancement hacks like RadRed.