The lesson to be learned is that it’s less risky, not more, to understand that some ideas don’t work out and to have ways to identify failures quickly.

I get and like that interpretation.

I wonder if, societally, it's true though, or if statistically the more reliable way to "succeed" in life, is getting good at selling and defending ideas, even the bad ones.

That only works if you lack a conscience. I think you were right to quote the word succeed!

For most people that lean heavily towards this (we all somewhat do, we all have our pride from time to time) it's probably not a very conscious decision. Framed slightly differently it can easily be made a virtue, for example "be headstrong" or "stand up for what you believe in".

It hard to spot, while/when you are doing it.

Not all advice applies all the time.

I think what you're talking about here "stand up for what you believe in" is maybe a position you should take with others.

While "kill your darlings" is a devil's advocate position you should take with yourself when you don't have someone giving you constructive criticism.

Yeah if your families income etc depends on it yeah its hard to take that many risks. Not everybody has enough wealth to prosper from the passive income such wealth could create.