Some of the "new physics" theories that receive the most academic attention are in my view, looking at the field from a "forest" rather than a "trees" view as an informed layman, very implausible. Here are some of the most notable of them.
1. Cold dark matter and WIMPS.
The dark matter paradigm is alive and kicking, but the "cold dark matter" paradigm that assumes that dark matter is made up of exotic particles of 8 GeV mass to hundreds of GeV, particularly "WIMPS" (weakly interacting massive particles) in that mass range increasingly appears to be at odds with data from astronomy.
2. SUSY, Supergravity, and string theory.
Most mainstream versions of string theory aka M-theory imply supersymmetry aka SUSY as a low energy effective field. But, decades of research later, the positive evidence for SUSY is still not there and the motivation for the theory is increasingly weak. Supergravity theories, which extend SUSY by incorporating gravity are similarly problematic.
Experiments at the LHC have pretty much ruled out sensible extension of the Standard Model with four rather than three generations of fermions.
This theory pretty much died when the Higgs boson was discovered. It had been a leading approach to explaining Standard Model data without a Higgs boson.
5. Anthropic Principal Theories and the Multiverse.
Cosmology theories that resort to explaining the current universe with the anthropic principle aren't really science in the ordinary sense.