Caterpillar

Having a working product that you can incrementally improve, can be a great asset in guiding further development. Especially, if it has real users, which provide feedback to you. (And that feedback might be that you don't like how they're using it, and you need to change direction.)

As I noted recently, this incremental approach might require taking a circuitous path towards your vision. You might need to implement things that won't make it to the final version (if there is such a thing), that take the project into a different direction for the time being.

I think all of this is worthwhile. It would be way worse to toil in secret for a long time, building something that you imagine will be good, but that nobody ever wants. Or build towards a big vision that you would otherwise have known is the wrong one. Or lose motivation because all you have is a lot of work and no pay-off.