There are probably at least as many reasons to changes Jewish laws as there are laws. But besides the changes themselves, I believe the motivations for the changes are also important. I'll give a respectful hearing to a proposed change to halacha based on a feeling that the present system give unethical results. I'll listen to a change that says that the underlying reason for a halacha has been disproven (e.g., prohibiting mixing meat and fish).
But I'll reflexively reject almost any halachic change proposed for the purpose of "ensuring Jewish continuity." To my mind such changes confuse the means of Jewish life with the ends. According to traditional understanding, Israel has a contract with Hashem. We keep following the halacha, and in exchange, Hashem ensures the Jewish people will survive. This halacha need not be static - I'm not saying all change is ruled out. But the change to halacha should be done by halacha means and for appropriate meta-halachic purposes. To change halacha to promote Jewish continuity means trying to own both sides of our contract with Hashem. This strikes me as both inappropriate and ill-advised.
Halacha is a system that is meant to show us the way we should live. We should change halacha because we sincerely think we've found a better way to live, not to game the system.
