If the secret sauce of unicorns were mere commodity shovelware, I would agree. There's nothing wrong with outsourcing non-core competency side jobs or commodity shovel work, happens all the time.
Or rephrased, is a tech unicorn not made out of tech?
I believe it is not. There is a user behavior and a data flow that go together to get traction. Marketing is probably the most important part. Luck being the 2nd. Tech may be way down there, alongside carbon paper.
Or rephrased, is a tech unicorn not made out of tech?