The Standard Model is a patchwork; it is a collection of theories under a single name.
Its best part of is the Electro-Weak synthesis, but recent experiments show that neutrinos have mass.
In the original Eletro-Weak Theory, the Nobel-Prized one, neutrinos ( electron, muon and tauon) were massless.
So, something had to be done to cope with the new facts.
It is easy: the solar neutinos have mass, but the Electro-Weak ones do not have it !!!
One kind of neutrinos is a "rotated" version of the other. ( See Griffiths 2nd edition ).
If you can not detect quarks, no problem: they are confined inside the hadrons; if you try to separate them
you simply create new hadrons.
All the Standard Model particles are said to have been experimentally found: the six quarks (never found alone) and even a Higgs-like boson, but several physicists are already speaking of a beyond Standard Model Physics.
Well, it seems that there is, still, a lot of work to do to fix the present theory.
Karl Popper criterium for a scientific theory requires that it must be falsefiable: the theory must predict a result
that,if not found, would reject it.
The way the Particle Physics is being done is no longer a scientific one: no matter which result is experimentally
found, it will not cause the rejection of the theory