Huh? That's entirely incorrect. There's definitely a middle class that isn't working paycheck to paycheck but can't afford million dollar homes, vacas and college for their kids.
There's also a part of that middle class who can afford vacations and college for their kids, but not million dollar homes. Even if that group is likely bigger outside of the US (since hey, college in European countries like the UK is damn cheap by comparison), it still exists over there in the US too. Neither of those things necessarily require a millionaire income.
To me the point is that "other middle class" you mention, call it lower middle class, is shrinking, falling into the lower class. Because of loss of decent paying factory jobs, retail shrinking, etc. If you are an adult today without special education, it's really hard to have a decent lifestyle. Most of my friends are programmers or teachers, and they most all of them have decent jobs. The teachers are increasingly in that lower middle class category. Software engineers are more fortunate.
We are, I earn significantly more than my partner who has a degree and I don't have a degree.
It's one of the last fields that without a degree you can still earn a good living if you can break into it somehow (in my case it was side gigs/contracting to crappy full time position to none-crappy full time position to decent full time position).
Though I'm in the UK, I gather the degree requirement is a harder line in the US, also worth noting that by and large university education has had no correlation with programmer ability (in business settings) in my experience, I've met good/bad with degree/without degree.
Interestingly the one correlation I have observed is how fascinating people find the field when they are children, young geeks become older geeks.
On an unrelated note, this is why I think the programs that encourage young girls to get into computing/programming are the ones with the best likely RoI in terms of re-balancing the field.
I think it used to be easier in the US to be a dev without a degree, but it's hard to get all the background to pass interviews without serious education, things like time complexity and their of computation.