Not necessarily, if at all. I'd say "optimizing" marketing will be difficult, but marketing and acquiring users is totally doable. The problem will be retaining those users, but that's ok too.
When your in the "hunt" (ala the search for product market fit) you need prospective customers to come and test your product in order to get feedback to find out what needs to be modified/created to hence find product-market fit... right?
So, spend some money marketing to get some users, hopefully you've got pseudo-product-market fit so customers will like what you have just enough to give you feedback to make it better, then iterate, market again, and see what they say. Eventually you can optimize marketing for cost and quality.