I always wondered if that kind of practice was bullshit by marketing people to justify their job or if it actually ever works.
The mere fact that one would need to create a fake landing page hints that the project is not solving an actual problem. If you only have minutes to spend on a side-project and don't immediately see whether or not it solves an actual problem, maybe just don't do it?
For example, you might have a problem that is worth solving just for yourself alone. In that case, you might wonder if it's worth creating a web UI around it or a simple script suffices. That depends on other people being interested on it or not.
Another case could be that you want to learn more about the problem before designing the solution. Should you really create a bad solution just to get in contact with the people that have that problem?
It's usually easier when people reach out to you for help with a problem they're desperate about. Instead of you cold-emailing randomly.
That's more or less the spirit of starting just with a landing page.
What's your opinion?
My opinion is that it must be hard to get visibility for a landing page to a product that does not exist.
Side-effect: I don't believe anything businesses say unless I can see an actual product, because such marketing schemes trained me to be suspicious of everything. Businesses lie, except when they don't (which is rare).
So maybe this kind of landing page “trick” can't bring you too far. But it can definitely help to see if there's someone interested at all.
Today, the landing generator service page has gotten ten-ish emails. For a product that doesn't exist and for someone without an audience (me). Another one I have has gotten 0.
I'm also suspicious of things like this as a user, but apparently not everyone is. Specially people that are really interested.
With tools like this, they will learn soon enough :-).
At a company I'm at now we just implemented a heart button on pages without it actually doing anything, except we track if people click on it or not. This is a smaller version of the same validation. If it's justified, we will build out the feature of liking things. Building out entire castles and worlds that no one lives in is very tempting for a passionate developer.
Months adding features for something no one will ever use.