Err from memory isn’t there a pretty clear definition of classes in a capitalist society. Initial definitions were lower class being people who derive wealth from selling their labour and upper class being people who derive their wealth from owning the means of production. Middle class came about when workers started buying/setting up companies so suddenly there were people who both sold their labour and owned means of production.

So regardless of what ever you think of your job, unless you own a company you are lower class. There’s probably a portion of middle class who would be on the edge but you’d think most should be resilient enough to weather most storms.

That said, if some dipshit in government makes some idiodic decisions then yeah, a lot of middle class people are going to find their stable businesses are a house of cards.