This is a variant of "eat your own dog food", but with a bit more nuance to it. Rob Fitz points out:
I've made this mistake a lot. I have an idea. I ask customers if it's a problem. It is. I ask how they currently solve it. Excel? That's barbaric. A better, more specific tool could exist, so I go to work.
In every case, the mistake was discovered when I began seriously using the existing tools for that exact use case. And I usually realise: they're not so bad!
One of the questions that smart investors will often ask is: how are power users solving this problem right now? The answer is never "they're not solving it", unless it's just not a real problem. Power users will always figure out ways to contort tools, processes, people - whatever is available to them - to somehow power through the problem and get whatever it is they want done.
Ideally, you should be a power user of your product. If that's not possible, then at least you should have such a user as a close advisor or even part of the founding team. They will be the ones who sit up in the brainstorming session and point out that the entire product is unnecessary because everyone solves it with a simple excel spreadsheet at the moment.
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