Fuji is obviously a volcano – and a barely dormant one at that – which means it has a caldera in the top, in this case 200m deep.
because of the conditions, we usually summit about once in every 5 attempts, so topping out is still something special and not to be taken lightly. to get there usually means a night spent on a windblown ledge in temperatures down to -30c, after carrying decent packs for around 1500m of gain, most of it on steep snow in exposed cold and windy conditions. if you cant carry a pack for 8hrs uphill, manage your gear at low temperatures, be confident with steep cramponing technique and cope with cramped tents, then fuji in winter is a good way to debug the system before heading on to bigger things.
trudging uphill is secondary to what makes Fuji a good training peak. its the ‘house-keeping’ skills that determine your success on big mountains – can you lay in a freezing tent for 16hrs? can you piss in a bottle? can you happily co-habit a small space? can you stay relaxed in high winds? does your gear work when stationary? what Fuji lacks in altitude and technicality it makes up more than enough in exposure, temperatures, height gain and gradient, all things better learned within view of civilization than at the sharp end.