I think that early traction is the key indicator of potential future success. Unless you're working in an industry where early traction is literally impossible to attain (pharmaceuticals, medical, VR hardware, R&D, etc.), the market tends to be pretty responsive.
If you're working on a piece of software, make a "free tier" open source version, give it out for free, get as many people to try it out as you can. If people aren't even remotely excited, pivot: it's not a good idea.
It's like fishing: if you're getting no nibbles, change the bait.