What you said is very true, it doesn’t apply to the cosmological constant though. It is not so much that we need it for a model to be in line with empirical ob

What you said is very true, it doesn’t apply to the cosmological constant though. It is not so much that we need it for a model to be in line with empirical observation, it’s that empirical observation gives one value and our models predict another value. The discrepancy is big and if we can’t make our models work empirical observations, that is really embarrassing. Regarding non-falsifiable theories; there’s not a physicist that thinks theories should not be tested. A lot of work is done to make these theories testable. Unfortunately, they are often only testsble on open problems since the limit of these theories just reduces to GR for instance.