I've seen several articles suggesting building a landing page to validate your product using a landing page. Some describe building a landing page for an existing MVP, others describe building the landing page before you even invest time in an MVP. So:
Have seen them and in a few occasions left my email. Most often I forget about them afterwards and don't do anything with it anymore, so lost customer. Would suggest to deliver something to your potential clients like a small ebook or some like that.
Having x clicks on a page does not mean much, see if people want to pay or really leave something like spending time on a call with you.
Btw I had one before and it was blocked by Google because the product was not there.