There's a possibility that the Standard Model may not be either correct (despite being very accurate) or complete: https://www.scientificamerican.com/...o-a-previously-unknown-force-in-the-universe/ At this point, the odds in favor of these experimental results are about 1/10,000. That's generally not enough to upend the Standard Model just yet but..?

As I understand it, the Standard Model has 26 or so free parameters, whose values have no theoretical basis but which appear to be arbitrarily fine tuned. A table of 19 of the parameters is given here: https://en.wikipedia.org/wiki/Standard_Model#Construction_of_the_Standard_Model_Lagrangian The table omits the masses and mixing angles of the three known types of neutrino - another 7 parameters. https://en.wikipedia.org/wiki/Neutrino_oscillation#Observed_values_of_oscillation_parameters At present, the Standard Model reminds some researchers of when Ptolemaic epicycles were used to calculate apparent planetary retrograde motion - quite useful for calculating behaviour to a first-order degree of precision but there are now apparently significant deviations from experimental observation. Perhaps we need a new Copernicus, Kepler, ideally a Newton, and eventually an Einstein to sort it out before we then realise there are new phenomena that require a new paradigm. http://motls.blogspot.co.uk/2008/07/myths-about-epicycles.html

Yep - heard some of this before. Basically, it's not a finished product, so to speak. Part of the issue seems to come from the fact that Quantum Mechanics itself is still very much in flux. Since the Standard Model is built on those foundations (clay, sand etc...) there's still a lot of work left incomplete. That's not to say that this is a bad thing in itself. That allows the concept to adapt and expand as new information comes in. Having it written in stone too early could easily be the death of the whole thing instead.

Quantum mechanics is a non-relativistic theory and does not apply to massless bosons such as the photon. The Standard Model is based on Quantum Field Theory, which has several assumptions baked into it that perhaps could do with some reexamination. It is, however, one of the most successful theories that we have in addition to those of General and Special Relativity in terms of making testable predictions. Unification of these theories so that gravity at the Planck scale is covered is problematic and it seems that we might have overlooked something crucial in the way the Universe works at extreme energies and the smallest scales.