Science educator Sabine Hossenfelder is a research fellow at the Frankfurt Institute for Advanced Studies. But Hossenfelder's latest YouTube video expounds upon the sorry state of particle physics, and in the process also has some interesting sidenotes on dark matter.She talks a lot of about models that expand the symmetry to some larger, possibly broken, symmetry. For example the grand unified theories combine the weak and strong interactions into a larger group. Supersymmetry also adds many symmetries, and so does string theory.
Hossenfelder criticises what has become the standard operating procedure of particle physicists, whereby they routinely predict the existence of particles that violate the Standard Model. Eventually, the postulated particles are experimentally falsified, at which time physicists move on to even more fanciful predictions.
Hossenfelder is pessimistic about the future of the field if particle physicists continue to behave in the same manner going forward. Hossenfelder also notes that in the past 50 years, only a handful of predictions have been validated, and all these were necessary elements of the Standard Model.
There is an argument for such theories that goes like this. The history of Physics is in finding broader theories that unify others. Newton's gravity unified terrestial and celestial gravitation. Maxwell's theory unified electricity and magnetism. They were truly unified in that a moving electric field would generate a magnetic field, and vice.
So it seems conceptually desirable to unify strong and weak forces, with a larger symmetry group.
But it is not. All these theories cause drastic increases in complexity, and in unknown parameters needed to define the theory. Having more symmetries does not reduce the complexity because the symmetries are broken.
With electromagnetism, the symmetry is real, and you can do away with magnetism, and treat it as a relativistic effect of electricity. With the grand unified theories, there is no advantage to the extra symmetry at all. It does not make the theory more elegant.
All of this would be irrelevant if there were experimental evidence for the unified theories. As Hossenfelder explains, many billions of dollars have been spent looking, and none found.