How can a startup understand if it's the right time for a pivot?
When is a pivot necessary? Before the MVP because of feedback on a demo? To help formulate an easier customer acquisition and sales strategy?
If, on the other hand, the demo is getting consistently negative (or "meh") feedback from prospective users, you may want to re-examine your value proposition.
Obviously, thinking about your customer acquisition and sales strategy is always a good thing, and if there are changes you can make to your product development to make those things easier, do it. Just remember what people say that they want isn't always what they really want-- which is why it's good to get the MVP out there.
That said, they might not be able to totally define how the product will be received in the market, but they might be right on the money about customer acquisition and sales strategy. The main feedback was to have a lower cost and more scalable sales and acquisition model. This is why a product pivot may be a good start, because the product in development now might not be able to successfully find a good fit with customer and sales strategies.
However, not having the MVP out there to understand how users interact makes a product pivot question harder to address.