Supplemental training for MMA=waste of time?

With so much to master in terms of striking, takedowns/throws, and the ground, does supplemental training largely waste a fighter's time that could be better spent on technical training?

Examples:
Conor McGregor doing "movement training" with Guru Ido Portal which included him burning out his shoulders on Olympic rings the same week of his loss to Diaz.

GSP's training track and field and gymnastics.

Many MMAers NFL style conditioning training.

Jon Jones year of powerlifting before a very lackluster performance against a mid level light heavy weight.

Cain's leg extension cardio-injury inducing workouts.