Mental Health and addiction treatment have to come first THEN housing.
Some people will struggle with mental illness and addiction their entire lives. Would you think it'd be easier to fight those things when you're homeless or when you aren't?
I'm Finnish. It's hard to even speak to some Americans, because I genuinely can't fathom some people who consider others to "belong on the street", "they deserve it" and one that has even made it some of my dumbo liberalist Finnish acquaintances "homelessness is a choice".
Ofc housing first works. Because it's not "housing first" in the sense that it purposefully houses people before getting them mental health or addiction help. It's "housing first" as in "having a place so you don't need to sleep on the street is a priority".
We have "housing first" (we don't call it anything like that lol) in Finland, and if you were homeless and extremely fucked up on a drug binge, you'd obviously go through a ward to handle the most acute effects and get you on a basic functional level, during which they'd probably communicate with social workers who'd get them some sort of housing.
The system is good but in practice people aren't perfect and both sides make mistakes; some people are too addicted and have problems and hard to be helped, but also sometimes the bureaucracy is fucked or some social workers / doctors suck.
Still, as long as those people have an apartment to go to, it's more or less fine.
People are rarely as fucked up as that, even actively schizophrenic people. (Like literally my upstairs neighbour. No joke.) You shouldn't use a psychotic episode to argue that housing being prioritised is a bad thing. That's just a non-sequitur.