I know you're not OP and I understand this is the definition of rent-seeking behavior, but your examples are empirically and theoretically invalid. Landlords (renters of capital) and middlemen provide huge benefits to society.

Of course, this doesn't mean that it's impossible for a landlord it middleman to be a rent-seeker, but they would need to pursue some type of artificial benefit/restriction on others in order for this to be the case. This does happen often, but I have no idea why OP would suggest rent-seeking is the primary activity of sharing economy companies. One of Uber's greatest accomplishments has been significantly weakening the rent-seeking taxi industry.