I agree. I find it hard to argue against the claim that all physics is just curve fitting. We always end up with tuned parameters to make the maths work. For example the G in F = Gmm/r^2 (Newtonian mechanics).

I'm not an expert, but it seems like Dark Matter theories allow the DM distribution to be tuned. Is that the case? Can you say, "oh, there must be a clump of DM over here with mass X". If so, that would give you lots of parameters to tune per situation you're modelling. It may be that IS how the universe works. The problem is that the theory is hard to falsify if it has so much wiggle room to fit every situation.