True, the Standard Model does explain a very great deal. Nevertheless it is not yet a proper theory, principally because it does not satisfy the physicists naive faith in elegance and simplicity. It involves some 17 allegedly fundamental particles and the same number of arbitrary and tunable parameters, such as the fine-structure constants, the muon-electron mass ratio and the various mysterious mixing angles.
Sheldon L. Glashow, Charm of Physics: Collected Essays of Sheldon Glashow
fine-structure-constant, fundamental-constants, history-of-science, physics, theory