Sorry, but what does it mean to "get serious about mental illness"? Everyone is already serious about mental illness. No one makes jokes about it or takes it lightly, say, like they used to in the 1970s or 80s.
Even how we refer to them has changed, and there are thousands of programs out there, many free, for people suffering from mental illness.
There are constant PSAs about suicide hotlines, mental help resources and so on, on radio stations and TV commercials.
Most corporations offer some kind of mental health resources. So I don't know what else society can do in the name of "getting serious" about this. It seems that contemporary society in the 3rd decade of the 21st century takes mental illness very seriously.
We seem to be normalizing mental illness as if that will cure it.
We ,as nation, do not like to force treatment or promote institutionalization any longer. Perhaps we should revisit those solutions. Expecting broken folks to fix themselves is a little far fetched without a stable home life. Some folks sadly can never be fixed.
What I mean is get these people help or commit them. They should not be out free to kill or, as they get older, living on the streets. Fix that problem and short of gange and criminal urban violence, we solve 99% of violent crimes.