You are missing one of (if not it the) most important step. After discovering a problem to solve, and quickly surveying the market for existing solutions and competition, you gotta dive head first into Customer Discovery. If you’re not familiar with this, study and practice stuff from Steve Blank, Rob Fitzpatrick, and Justin Wilcox. Learn about the customer development process, focusing on doing discovery work with early adopters. This is the first step to executing well.