You are building to solve their problems or open up their capabilities, and if they knew how to do it, they would have already. So listen to your customers for the "why", but use your own judgment for the "what" and the "how" of it all.

And be honest about being differentially valuable. I once had a prospective consultancy customer ask me for a very specific and elaborate piece of software to be built. He'd been thinking about it for years. I dug in on what he was actually trying to achieve, and I realized that small modifications to an existing in-market product would be able to satisfy his actual needs. I connected him with that company, he ended up with exactly what he needed, and they ended up with a high-end expert user as a resource.

Of course, I ended up putting myself out of a lucrative consultancy job, but I don't regret the decision at all. I suspect that most folks on HN feel the same way. Find a way to make a difference, and be honest with your customers (and leads) about what you're bringing to the table. That kind of integrity pays dividends in the long run if you have something truly valuable.