A waitlist signup is a weak signal: it costs nothing, commits to nothing, and a well-designed page can collect emails for almost any idea. If the page exists to decide whether to build, make the signal harder to fake and read it honestly.
Three things strengthen it. First, send cold traffic, not friends: a small paid test to strangers who match your buyer tells you something; a post to your own network tells you that your network likes you. Second, ask one real question after signup, such as "What are you using for this today?" or "What would make this a must-have?" The share of people who answer, and what they say, is more informative than the signup count. Third, offer a stronger commitment to a subset: a short call, a paid pre-order, or a deposit, and see who takes it.
Then read the result as a stranger would. A list built from a reward-heavy referral loop measures interest in the reward. A list built from a vague headline measures curiosity, not need. A list built from a precise problem statement, cold traffic, and one honest question is as close to a demand signal as you can get without a product. Score the page on clarity, proof and friction before you run traffic, so a weak result means weak demand rather than a weak page.
Before you spend on traffic to test the idea, run a landing page audit so that a low signup rate tells you about the market rather than about the headline.