I think the issue is how it's phrased. OP said, effectively, I don't like my job, should I do a start up? Which is a terrible starting point for a business.

I think the issue is how it's phrased. OP said, effectively, I don't like my job, should I do a start up? Which is a terrible starting point for a business. If they said something like "I've got this great idea" then people would tell them to go for it. There's this weird idea out there that Start Up is a job or company in itself. But it's not. Sure, companies will pivot and opportunities can come out of seemingly nowhere. That doesn't mean you just start something without a reasonable belief that it will work.