They are _not_ doctors in terms of evidence-based medicine, just policemen without a token. The problem is obviously not about incorrect diagnosis, I can lie to any doctor about any symptoms and just go home with zero obstructions from feds.
As someone who was formerly in a mental ward for acute crisis, I would say that at least the 72 hour hold was an essential and necessary part of my treatment. I don't think that staying at home with unprepared family members for the acute period would have worked out, and I don't even have a problematic home environment!
The flip side of the coin is that I was in a really high quality hospital, I'm sure there are hospitals or facilities that can be more harmful rather than helpful.
I also have a problem with the way that they treat mental health like cancer, that once you have a diagnosis you will always have it. There are zero diagnostic criteria for "fully recovered" or removing dependence on medication, even after 5 or 10 years. It's also treated like a scarlet letter for insurance and unrelated things like TSA pre check - no matter how well you are doing you are still some level of risk to yourself and society. Though I could be wrong... the reoccurrence chart over time for my specific acute mania (with no depressive episodes) does look a lot like cancer remission charts with asymptotic approach to 80%+ reoccurrence after 2-4 years.