The worst advice for a startup founder.

"Don't do it"

"Focus on features, customers don't know what they want"

Quit your stable job and go all in before anything is proven or there is any fundraising interest.

"Don't tell anybody about this"... I think this is bad advice. Even if you're working on GPT-5, there's a good chance the people you'll talk to about your new idea will either not care enough to pay attention or just don't understand it at all. But there's a slim chance that somebody who you share your idea with will become your partner/co-founder/investor, etc. This was the case for me and ever since, I am always happy to share my ideas with everybody.

"Just follow your passion". No doubt passion is important but it's not enough