I'm no fan of the ACA. It was a bill written by corporations for corporations. It didn't solve the issues with American healthcare.
When it comes to the middle class' downfall though, that's really not the problem.
It's just plain impossible to make an argument connecting Obama, the ACA, and harming the middle class when the trend for health care costs has been absurd for a while.
(I totally agree that rising costs are harming the middle class, but for me the issue of tens of millions of people not getting decent pay raises is far more indicative of an economy not paying off like its supposed to.)
Until someone has explanations for the incredible pace at which people's skills are being rendered obsolete (and thus not worth a respectable wage), I'll continue to point to it as a main culprit for the middle class' extinction.
The problem there is that the majority of people just don't have what it takes to be a competent engineer. We need jobs for average Americans too, that's the middle class were talking about.
STEM jobs are super, but at the end of the day if there aren't decent jobs for people with an associate degree, high school diploma, or non-STEM bachelors then we're pretty screwed. We simply can't have an economy in which it's "upper middle class or GTFO."