Of course it's Subjective, but you can be Subjective and wrong.
How many Americans don't think they're overweight?
How many people have to work until their deaths or retire in absolute poverty because they have literally nothing saved?
There's a fair amount of people who are some shade of okay.
But there's a lot more who are in dire circumstances
Sure, and I'm not disagreeing with your point. Rather I'm casting doubts on the relevance of the "data" being presented, which is (as far as I can tell) entirely driven by opinion and context, and not in any way normalized.
To me the most you can read from it is that a lot of people are saying "I'm doing OK by the standards I set for myself, but I recognise that a lot of other people are struggling". Which doesn't seem like an entirely unfair position, although it does raise one rather obvious statistical issue - if 20some % of people think they're not doing financially OK but over 50% of people think that other people are not, then clearly there's about 30% of people who say that they're doing OK but others think they aren't. Which then raises the question as to whether the issue is the self delusion of people who are struggling but think they aren't, or people assuming that others who are actually quite happy should be doing better.
There are a lot more questions and uncertainties in that tweet than there is anything of any real value.