Its just a part in the equation where you're dividing by zero, that's all. We know you cant divide by zero, so it means our theories are incomplete.

The gravastar theory is notable (IMO) because it does away with the singularity. Although, it seems like this theory is borderline unfalsifiable, since any way you could detect a gravastar would also be insistinguishable from a black hole.

Personally, I am of the (completely unsubstantiated) opinion that black holes create universes (somehow) because it is a simple, succinct answer to many questions. So, any theory that takes that seriously would be worth further research, imo. But until there is some kind of observational evidence, I think this is just relegated to the realm of "that's a neat thing that math can do".