[mooted1]

This kind of analysis nearly always fails to account for why these businesses aren't able to recoup expenses. While many startups are will never find a large enough market to be profitable, many others choose to invest earnings and take on debt in order to improve their product further and acquire market share.

Could Uber or Lyft be profitable if they slashed incentive spending, cut R&D efforts (self driving cars, improved matched algorithms, etc), closed up shop in cities too small to be profitable, and fired everyone that wasn't critical to keeping the business running?

Maybe. But this guy certainly doesn't know enough to tell.