I kind of agree but I think you haven’t exposed the real root cause of the issue.
SV can always trace it’s faddish behaviour back to a few key individuals. The rise of stoic philosophy is definitely due to the popularity of Shane Parrish newsletter. I love Farnham Street and think Shane is engaging and well read but it is his passion. Anyone simply reading the stoics because Shane or Ryan Holiday said to do so is missing the point. Shane and Ryan are not reading stoic philosophy because someone else told them to do it. They are advocating it due to its applicability. If Ryan Holiday was gripped by John Grisham and sold JG novels then Silicon Valley would listen.
It’s the finger pointing to the moon and missing all of the heavenly glory.
The other root cause is that for a small minority of start-ups; they will genuinely be on a world-changing mission. That success requires prioritisation but it’s prioritisation for something they love. The aeronautics of SpaceX, engineering at Tesla, the big data capability of Palantir, the original Macintosh team at Apple.
Non world changing start-ups see these habits and adopt them for less worthy goals thinking that it is the key to success when their own app or service would be just as well served with a normal working week. So they eat Soylent while building the latest submission to Product Hunt for an app that lets you track your pet rather than because they are trying to revolutionise space travel and are grappling with the hardest engineering problems in world history.