I am writing from a U.S. perspective. This actually goes back a long time. The Jimmy Carter Administration tried to introduce a public health model, here: "Rather, the change of terms was based on the application of a public health model that emphasized the role of the environment, social services, and prevention rather than the traditional psychiatric focus on the diagnosis and treatment of severe and persistent mental disorders." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2690151/#!po=8.46774
During the Reagan administration, Carter's legislation was repealed and a system of block grants was instituted, many public psychiatric residential facilities were closed down; many of these people migrated to the streets and public libraries, so we had librarians acting as "psychiatric nurses". It was a complicated issue because the public long-term residential facilities for the mentally ill were not that great, many people were simply tranquillized and put to bed; so the Reagan Administration was not completely wrong, but they just shifted the problem as I mentioned above to the streets and to inner-city libraries. At any rate, deinstitutionalization was already under way when Reagan took office, timeline: https://www.motherjones.com/politics/2013/04/timeline-mental-health-america/
Karl Mannheim had some good ideas after WWII. (1950) His book is interesting: Freedom, Power and Democratic Action. There is an old review of this book by Commentary magazine on the web.
Of course times were good and no one listened to Karl Mannheim after the war, certainly not in the United States. No one wanted to plan for a better society.
What do we call these things we have in the U.S., mass shootings? This started to my memory with Charles Whitman at U. Texas (1966). Elton John has a song, "Ticking" (1974). "It may be that lyricist Bernie Taupin was inspired by the Whitman shooting, albeit indirectly." (Songfacts)
Might things get better if we let things get worse? Oddly, yes. Maybe we will finally wake up as the madness increases. As it stands now the short attention span of the public and the media acts to push the latest violent incident under the rug.
In the meantime, who wants to take a bullet from one of these shooters? How does nihilism factor into this? We know today that many of us, not all of us but many of us, are postmodern individual monads without community. No religion and no replacement for religion. No overarching narrative. Loneliness. We can't seem to get on the same page. The only narrative we have is Star Wars and I lost interest at part II, whatever it was. I forgot Batman. He must be mentioned. Of course some philosophers think it's a good thing that we don't have a meta-narrative, because it is a form of dominance, an exercise of power over the masses.
Foucault wrote about mental illness and power. Erich Fromm had some ideas. Even Konrad Lorenz in his later works spoke about where man was headed. I must also mention Allen Wheelis, "The Way We Are", 2006. Many others. The problem is with society, and to fix things means to stir up society. For the time being some people can hide away in gated communities, and enjoy the benefits of "security". I think they are fooling themselves.
I do think what the OP suggests regarding mental health would work in small and medium communities as long as they were given money and allowed to do their own planning. However, in the long run we must face up to what this quote suggests:
"It is no measure of health to be well adjusted to a profoundly sick society." Jiddu Krishnamurti