Great read, Linda. This reminds me of one of my huge pet peeves: relationship advice that is, in fact, toxic. A couple weeks ago, I wrote to Medium to recommend some kind of flagging process and disclaimer banner, much like you recommend here. I hope they take it into consideration.
I personally think the situation is very nuanced: as someone with a graduate degree in sociology and demography, I'm no stranger to seeing people without a similar background opining on sociological topics. (Everyone lives in society, so everyone fancies their opinions on the subject to be "qualified.") Some of what people say is sound. Some of it isn't. Alas, ALL of it has the potential to impact public welfare, because content about society influences voting habits, and voting habits influence policy, and policy largely determines quality of life... and so on.
Which brings me to this food for thought: EVERYTHING we read has the potential to impact our mental health, physical health, finances, etc.
That said... I wholeheartedly believe that not all writers need to be trained experts in the fields about which they write in order for their voices to be valid, helpful, or healthy. Particularly when they're not posing as journalists. But as for the problems of this platform, the proliferation of people throwing diagnostic labels around is alarming, and the misogyny that masquerades as dating advice on here these days makes me want to scream. Also, I'm a deeply spiritual person, but my background involved years in the ivory tower, years of therapy, years of being a (trained) volunteer at a mental health organization, and continued work with academic researchers and their manuscripts — so I'm a grounded mystic, if you will. As such, it troubles me when I notice how much of the (popular) spirituality content on Medium looks like undiagnosed/untreated psychiatric struggles masquerading as "spiritual truths." (Aaaaaand, even though I skip past much of the finance content, you're right to call out a lot of that stuff too; I have a close friend who, thanks to unqualified internet blowhards, is now convinced he should gamble as much as he can on the crypto market because he's SURE it's his ticket to never working again. It's scary and sad. And I'm sure he's one of many.)
Long story short: I would not like to see Medium prohibit all-but-expert voices or pigeonhole us into the lanes that our degrees (if we have the privilege of having obtained any) are in, because I believe there are plenty of people for whom emotional intelligence, life experience, etc. genuinely can and do translate into legitimate, healthy, life-enhancing insights....
But holy shit, you're absolutely right that we need WAY more quality-control on this platform.