The standard model has a number of free parameters [1] but the results of calculations are pretty sensitive to them, and this is what predicted (not just explained post-hoc) the Higgs. It's not incorrect to say there's curve fitting involved, but it severely understates the magnitude of the achievement that is the standard model, and its success in explaining everything that underpins everyday life[2], as well as most things beyond that regime[3]
[1] https://en.m.wikipedia.org/wiki/Standard_Model#Construction_...
[2] https://www.preposterousuniverse.com/blog/2010/09/23/the-law...
[3] https://physics.stackexchange.com/questions/128374/evidence-....