You know what would fix so much even if nobody believed in registers or science or climate change? This: Everyone needs to be able to go from softer to louder and louder to softer on every note in the center 12th (or more) of their voice without cracking. Not without color change, but without bumps. If we could all do that, we would be damn far along. The proof and the method is so simple. It’s the training that takes so freaking long. If everyone worked on being able to do that, the belief system would hardly matter.
From Isaac Nathan’s Musurgia Vocalis (1836, p. 153):