If you have undertaken a thru- or section-hike of another high route — such as the Sierra High Route, Kings Canyon High Basin Route, Pfiffner Traverse, or Wind River High Route — then the Yosemite High Route will feel familiar.
These routes all involve extensive off-trail travel, substantial vertical change, prolonged exposure, and high altitudes. The most difficult sections are the passes, which are usually Class 2 (but occasionally Class 3) and which are often bordered with tedious talus. Technical equipment is not necessary, although lingering snowfields may warrant spikes and an ice axe early in the season.
Long-distance trails in the High Sierra and broader Mountain West — including the John Muir Trail, High Sierra Trail, Pacific Crest Trail, and Continental Divide Trail — are valuable stepping stones to the Yosemite High Route, but they do not teach all necessary prerequisite skills, notably off-trail navigation.
Furthermore, I have watched many strong on-trail hikers struggle physically and mentally with the route’s rigor. Off-trail travel requires more strength and balance than on-trail hiking, and it does not allow for mental auto-pilot. The vertical relief can also be demoralizing, because so much more effort is required to hike the same horizontal distance.