You can make the claims of your original post (and arguably more effectively) without the subjective (and rather idiosyncratic) view that GR was in some sort of indeterminate level of credence until the detection of gravity waves.
Sorry, I wrote poorly. I don't mean to say that GR or gravitational waves were in some sort of indeterminate level of credence. I mean to say that our credence in gravitational waves in the absence of experimental confirmation is justified by exactly the kinds of non-empirical evidence that Hossenfelder rejects. So it's clear that she's being too restrictive in what she believes is worthwhile theoretical physics.