It predicts things we’ve already observed, sure. But we came up with the standard model after seeing what ideas worked and which ones didn’t, and we get to amend it every time an experiment shows us something new.
The standard model isn’t some single theory that was devised and survived testing. It’s an amalgam of various ideas which have survived experimental verification. It’s a bit hollow IMO to say it “predicts” things. It’s a bit like drawing the dartboard after throwing the darts.
It predicts much more than what has been put in. The SM has 22 free parameters. I agree that if it predicted exactly 22 data points it'd be a pointless encoding of what was put in. But it predicts thousands and thousands of data points, some to twelve decimal points.
It predicts things as-yet-unseen, also, such as detailed proton structure, precision atomic matrix elements, detailed nuclear structure and decay rates, and so on.
Neutrinos were predicted and discovered long before the standard model.
Note that the standard model did NOT predict neutrino mass. Though it did predict that neutrino mass would explain the shortfall of observed neutrinos from the Sun.
