There are two sides to mental illness, the individual who suffers from mental illness and the people around them who suffer. This is a social issue that needs to be addressed by governments. Better healthcare including mental healthcare so everyone benefits.
I do agree with that, its often something that's not considered a lot by politicians, the public at large, even some professional groups too.
Something I remember being very aware of when training in social work was that the role of social workers, whether they were public servants or NGO employees, was that their interventions, assessments, plans were always meant to be time limited actions in response to breakdowns in informal support networks, like families, or more broadly speaking families, neighbours, schools, communities etc. The primary objective could be safeguarding, or identifying accomodation or some sort of care provider but the secondary one was always restoring the informal network to full functioning status and a tertiary objective exists the whole time of raising awareness of existing informal networks or trying to build them up some how.
I probably dont need to level with anyone that not every professional thinks that way, some think there's no one like them and no one can cope (or should even try) without them. Ivan Illich wrote about this in his book about disabling professionals, he also wrote another book called medical nemesis which makes some of the same points but also makes other points about unrealistic expectations of medics and medicine more generally, I share a lot of his skepticism about experts and expertise.
I also still find some of Erich Fromm's observations, like the "caring sadists" in Fear of Freedom, who seek out and perform care functions because the sick are at their mercy or within their control, scarily accurate in some instances.
There's a few scary stories from within the UK of those types, Harold Shipman was a doctor who administered lethal injections on home visits to vulnerable elderly people, there was another care assistant who tortured residents and staff in the residential home he worked in by administering insulin to them, another case of a nurse who killed the babies in their care. In Japan I think I remember hearing about some care assistant who massacred people in his care with a sword.
So informal solutions can be preferable to simply creating a strong institutional response which attracts shady types to it who can exploit it in wicked ways. Still that's far short of what Bush Did 9/11 recalls but its still an issue.
Plus, not for all because there's the thorny issue of hereditary make up, but a lot of people would benefit from much more broad public expenditures than simply funneling money to psychiatric and psychological services, inadequate education, housing, utilities, roads and other public goods, the stress of relying on those or even providing them, especially were you are not content to say everything is fine when its not, all takes its toil and causes people to become unwell.
Then into the bargain you've got managerial culture and business culture for most people who making out as employees, do they work for organisations which are fine examples of the Dunning-Kreuger effect? Are they likely to find other sorts of work easily if they do? Is their organisation full of people like those featured in movies like Horrible Bosses or whose main model in terms of management has been someone mainly influenced by reality TV, scandal and office politics? I dont know how you necessarily police those factors but they are big factors. Social issues not necessarily easily corrected with public money or services.
Finally, crime, war and violence, how much of it is there, its no mistake that people suffering that or with an expectation of the same are liable to become unwell or develop disturbed traits. One of the most important, probably the single most important, factors in recovery from trauma of any sort is a place of safety and the experience of safety.