You don’t need everything, everywhere all at once.
You don’t need to go full waterfall.
You do need to know what you’re building.
Why you’re building it.
And who you’re building it for.
If you’re not answering those 3 questions and keep trickling out the information as you receive, what you’ll end up with is a trickled-down app that kind of does what you want, for some of the people but they don’t know why it works.