A couple of problems:
1. You have a pretty high opinion of our police if you think that police unions, donations, and endorsements don't have effects on political campaigns, that towns don't use both police fines and public prisons as a revenue source, and that the criminal justice system can't have comparably (or even greater) negative effects as involuntary mental health interventions.
2. You have a pretty low opinion of our current medical industry if you think that it hasn't improved itself over time. Our country used to lobotomize people and commit them for being gay. Things can and do get better over time. That doesn't mean there aren't still problems, there definitely are, but even in just my lifetime, the way the medical profession approaches mental illness has gotten much, much better. Absent some kind of better data, I am skeptical of the claim that our medical industry's problems are being solved significantly slower than our (also numerous) criminal justice problems.
3. It's possible that this will lead to more medical involvement, but I would be cautious about making strong claims about how much that will be the case and what changes that will have in people's outcomes. It's important to remember that prison is really bad. As just one example, being convicted of a felony removes 13th amendment protections, which is regularly exploited for both private and state revenue -- even in public prisons! What data do we have that indicates that mental interventions will increase at a drastic rate because of this, and what data do we have that says that involuntary incarceration is worse than our current prison system?
4. Denver hasn't gotten rid of its police, it's merely changed how it's using them and how quickly they respond to problems. So it's not that the only tool is a hammer, police officers can still respond to situations. I think it's early to jump to the conclusion that the city is going to start thinking that involuntary mental interventions are the only tool at its disposal. I don't see strong data that backs that conclusion up; in fact 35% of the calls to the STAR program came from police officers. Another way of looking at the data might just as plausibly be that the city was treating police officers as its only tool, and now it's striking a better balance and realizing that arrests weren't the only way to deal with every problem. That's the kind of thing that'll get revealed one way or another as we get more data.
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> despite having no track record of actually being able to fix any of these ills?
Finally, again, just an unrelated side note, but I know people who are extremely grateful to both psychological therapy and psychiatric help in managing conditions. If you're struggling with this, you don't need to do it alone. Professionals can help. The idea that the only thing a psychiatrist is ever going to do is turn you into a zombie with drugs is bullcrap. And it also ignores that non-psychiatrist interventions don't always need to involve drugs. Cognitive behavioral therapy can have amazing outcomes.
I get that you don't have a high opinion of psychologists or psychiatrists, but they do help people. I just want to make that point very clear.