Some predictions of the model were tested soon after Einstein published the theory. Others, like gravitational waves, were not. Yet people still believed in gravitational waves long before they were empirically confirmed.

I don't see any possible basis for that belief (at the time) other than arguments based on non-empirical reasons like consistency and parsimony. (That is, it would be strange if other predictions of the model worked out but this one didn't.) Yet it is exactly this kind of theoretical reasoning that Hossenfelder, taken literally, seems to reject (in the absence of experimental data).

I'll also note that any other solution of the black hole information paradox has to be consistent with the the rest of what we know about physics, and any future empirical observations. So it can't be completely untethered from reality; it makes testable claims in this way. Further, it's not clear such solutions can never be directly tested, or will never be found to imply novel testable consequences.