LMA: Like GAW said, the RY’s can decide their criteria. Nevertheless I agree with you that everyone (bar none) has a right to learn in Kollel their entire life. It just that not everyone has a right to the elite Yeshivos. There are many others to choose from.
GAW: Brisk is an elite Yeshiva (to take one example). I don’t think I necessarily agree with your idea that the elite yeshivos are only for future gedolei hador. I would be more inclusive than that. Nevertheless, perhaps as you suggest some of the elite Yeshivos can indeed cater to future gedolim.