Is There a Way to Validate Product Ideas?

I was I was consuming a lot of thought leadership on different ways to validate business ideas or like test MVPs and a recurring one I heard. He said if you go to your target audience and you say hey like what do they think of this idea everyone's like this is a cool idea. Can you get people to actually join an email list or a wait list or things because people just giving feedback and raising their hand. It's like amazing the number of people that will not come through and end up buying later on when it comes time to ship the product.