Wrong feature, wrong customer, wrong price — chosen early, discovered late. You find out after the launch that didn't land, after the rebuild that didn't help, after months you can't get back.
Big companies have a job whose entire purpose is preventing this. It's called product management: figuring out what customers actually want, what competitors are doing, and what's worth building next — before anyone builds it. People who do it well make $130,000 a year and up, because the companies that employ them ship the right thing more often.
You don't have one. So you've been doing that job yourself — in the gaps, on instinct, with ChatGPT open in another tab telling you every idea sounds great.
Building faster just means discovering faster that you built the wrong thing.