Stellar lifecycle models are based on a combination of theoretical physics, experimental physics results that set bounds on (in a way) the theoretical predictions, and mathematical modeling - all of which is also validated through observational physics of stars that are, actually, at the red giant stage, and sampling stars at the intermediary stages - based on actual observations.
Armed with all of this data, and working on an assumption that current ‘laws’ of physics will continue to apply in the future, scientists can make reasonably confident predictions.
Similar approach, though admittedly with far less mathematical modeling, is also the case in biology.
Even textbooks and scientific resources have to assume, at some point, that we start with a framework of axioms.
But most science textbooks also first introduce the idea of models, hypothesis and the notion that a ‘law’, is only as good as the most recent experiment that supports it - and that the scientific method requires us to discard or amend the ‘law’ if new evidence contradicts its predictions. To keep repeating this foundational idea every step of the way seems tedious - it’s reasonable to treat gravity on earth as a fact in the face of overwhelming observational evidence, for instance.
I don’t see how any of this reflects hubris and unwillingness to admit what we don’t know.
For instance, as an (ex-)biologist, I completely agree we do not have a good model for consciousness; or that we simply don’t have a solid functional model of a cell that allows us to model and predict its behaviour at detail and with all its complexity - we are still, in fact, discovering layers of complexity and nuance. But there are some things we do understand well.
Same in physics - the search for a Grand Unifiying Theory continues. ‘Dark matter’, as I understand it, is an acknowledged proxy for many things we don’t yet understand.
So..not sure I agree with your position :)