yet another "I've got nothing to show yet but gimme your email to eventually know more later". Yawn.

I hear ya, but it's the easiest way to gauge interest before putting too much time into a completed product.

yes, it's the easiest way if no one else is doing the same thing.

But if there are a bunch of websites like these, which do the same thing and no one ever receives as no communication any time soon, no one's going to believe this has better chances than other.

At which point it's just a pain in the neck to signup for these.

gauge interest for what? No mockup, no screenshot, no detail, there's nothing to be excited or meh about.