The big dreams for your product are understandable. But a roadmap won't help, it will just make you waste time on planning a future that you can't possibly plan

The big dreams for your product are understandable. But a roadmap won't help, it will just make you waste time on planning a future that you can't possibly plan. There's another way. Think of this exciting vision first. Then, instead of making a roadmap and starting years of coding to finally arrive at this vision (which will never happen, likely), start cutting away stuff from your vision. Cut away non-crucial stuff, but keep that 1 or 2 features that are exciting. Search for what makes this really exciting. You don't need picture uploads. You don't need 90% of the features. Now build this core product. The core value. The exciting experience. And resist the urge to add stuff to it, instead cut more stuff out, even stuff you've already built, and keep improving this core thing.