And
There really is no counter-theory. “The knock on YC,” Andy Weissman, a managing partner at Union Square Ventures, told me, “is that on Demo Day their users are just YC companies, which entirely explains why they’re all growing so fast. But how great to have more than a thousand companies willing to use your product!”
https://www.newyorker.com/magazine/2016/10/10/sam-altmans-ma...
The long term effect is that, owing to the costs of the compute hardware all this runs on, all of these services become profit centers for Google, Amazon, and Microsoft who control the cloud services backend world.
The long term consequence of this is that as capital gets concentrated into fewer and fewer hands, so does the means of production. If you are outside the network you will find it very hard to sell your services even if you have a better product. This already happens in many places with wealth disparity. Deals simply do not happen without the "blessing" of a wealthy backer. Software is unfortunately moving that way. The once upstart nerd who was able to launch their business from the basement has turned into the technocrat baron who will keep such a thing from happening again.