So, bitcoin is about believing and trusting people?
Exactly, instead of trusting a group of bankers you trust a group of developers, then this is not a trust-less system
The problem here is that an open source project does not take any financial responsibility
At enterprise level, if a company push in a software change which resulted in customer loss, the company will have to pay the fine/compensation to customer based on the service level agreement or similar contract. So there are usually strict change and release management procedure in place to avoid such kind of loss as much as possible
However here in bitcoin world, there is no such kind of financial responsibility. If devs push in a change which resulted in customer loss, the devs are not responsible for the damage, or to say, they don't have enough money to compensate the loss from millions of users. The users are all on their own
Imagine that in future if pension fund and social security fund are all invested in bitcoin, and devs pushes out a change and let their bitcoin stolen, who is going to compensate for the losses caused for millions of people that relies on these funds for their retirement?
Of course no one can insure against everything, there is always risk, but it is a general practice to not take drastic change in financial projects unless in a crisis, and we are far from that yet