[bonzoesc]

How is a web form going to give you any useful data about demand? There's no investment or interaction with actual users. If you want to assess demand, make a minimum viable product.

[ed209]

You don't need an mvp to asses demand. Go on forums, get out on the street and ask people.

1) Get them to agree [or disagree] that the problem exists.

2) Explain your solution and get a reaction.

You should already have some idea of demand before you write a single line of code (other than the code they wrote for this simple page)