But what about their two year head start? If everyone is executing at the speed of light, there will still be winners and losers

It was always relatively easy to copy many SaaS services, especially bootstrapped ones. Unless everybody wants to make and run their service locally, very little changes.

Did you claim the same a year or two ago? Why or why not?

Yes friend. That's what people said 2 years ago. Next?

And? How easy will it be to iterate the product and build features and a user experience as it is used in the wild? How easy will it be to find customers willing to pay you money for it?