Ask HN: What to Do at a Stagnant Startup?

I have worked as a tech lead at a startup for just over 2 years now. The product is targeting the enterprise space and we've been in talks with clients since I joined but haven't had a paid pilot project yet. Clients put us through their preferred supplier programs and audits, but nothing comes of it. We've won lots of awards, we've been on accelerators/incubators run by potential clients, we're "in the process" with pretty much all the big players.

We've recently raised more funds and are growing the team. Investors seem to have faith, even though we're pre-revenue, but frankly I'm less optimistic.

I feel like we're building something no one may ever use. We don't have users for the product we're monetising and there isn't much in-house industry knowledge, so we may be building something no one wants. We could remain in the sales process forever. This is really demotivating and I'm not the only one who feels so. After the fundraising, we're trying to grow the team but it feels surreal building and growing this system that no one is using.

Has anyone been in a similar situation? I am thinking about jumping ship, but I feel some guilt as my leaving would be a big blow to the company. The equity I have would barely compensate me for the reduced startup salary over 3-4 years and that's if we exit.