What's this argument?

It's thin because we don't have enough data to say otherwise and everyone else is doing worse? Go get more data then before negating the signals and the two confirming data points we have. I "don't buy" is not a reason. It could be everyone is doing worse and men are doing worse than most (or impacted the most), those are not mutually exclusive.

It's not just that we don't have a lot of data, it's that the only area about youth mental health that we actually do have a lot o data about is the suicide rate, which is decreasing. It's increasing in America, but it's increasing for everybody, not just young people. There's no clear youth-specific decline in mental health except a vague increase in teens that report feeling that their mental health is poor, but this is plagued by bias. I don't think the problem is that we don't have enough data to say if the youth mental health crisis is real, it's that I think we have enough to say that it isn't.