So it's not that auto-update is flatly a bad idea, it's more that it's a trade-off that sometimes makes security issues almost evaporate, and sometimes makes them impossible to dodge.
What are the odds of one dependency being taken over by a shady anonymous entity?
We have seen bad updates breaking the entire Javascript ecosystem, but they were not intentional.
All it takes to inject a bad dependency is a burned out developer willing to delegate his free project to someone else...
So in practical terms, my experience is that vanishingly few people will behave differently than an auto-update system would behave, except in rare occasions like a malicious update making the headlines. We definitely need a solution for rejecting malicious updates, but I feel backing away from auto updates throws the baby out with the bathwater and would be a net-negative change for the industry and for users.
I don't envy Chrome leadership's decision or having that problem to solve.
Without automatic updates, you might be more inclined to put off a patch which turns out to be urgent. Or you might be more likely to lose track of which patches have been applied across your various systems.
Upgrading manually regularly: Good idea.
Having a cronjob to do it automatically without user intervention: Bad idea.