My 2c regarding Sierra's remoteness from an ousider's point of view (Boston).
Last year we didn't look at the map in time (stupid me) and instead of crossing the Snowtongue Pass we went over the col to the NW (loose and steep) and found ourself at the beautiful and frozen Payne lake. It wasn't that far to walk to Piute trail via Saddleback lake and Golden Trout lakes but it felt that people rarely go there - we did not see anybody.
Another time (maybe 6 years ago?) we did a chunk of Roper's route from Merriam lake north via Bear lakes and exiting at Mammoth. We saw exactly 1 guy during our 4 days off trail.
Both times it was a bit early in the season (late June/early July). Anyway, my impression of Sierra that it's far from being crowded. Just need to stay away from those trails.