Who said anything about blind or tradition? That seems like stuff you injected into this convo, not me.
I trust institutions who have a strong track record of predictiveness and desirable outcomes. Vanguard has both in spades, and has earned their authority. If they stop accurately predicting future behavior and/or stop producing desirable outcomes, that will change their authority on matters of investing.
Not trusting predictiveness and desirable outcomes seems prone to bias. If your alternative is that you only trust yourself, that seems like both a paranoid and privileged outlook, given how much time and how many resources you'd need to expend to gain even half of the knowledge Vanguard as an institution has about operating as an investment advisor.
