He didn't deny their existence, he just said he doesn't believe. Einstein himself had the same opinion, despite discovering some of the equations.

And, tbh: since the model says to divide by zero, that's a perfectly fair stance. "Black hole" might be erroneous terminology for these objects that we're now detecting.

I think the model is correct myself, but it is incomplete. We definitely don't have a good idea of what dividing by zero even means.