This is a common pitfall that plagues most developers who want to become entrepreneurs.
The idea is only one among several important factors that lead startups to success: timing, competitive advantage, finding the right product-market fit, identifying customer acquisition channels, devising creative ways to get the word out (aka viral loop), testing hypotheses early on, etc.
The number of startups with awesome ideas that have failed because their founders ignored all other variables is too large to ignore. Of course you don't hear about those as much, because (surprise surprise) the media feeds off success stories.
Please don't help propagate the idea myth.