I don’t think you’re being disingenuous here and English is a crazy language, so here’s the definition google came up with:
noun: capitalist; plural noun: capitalists a wealthy person who uses money to invest in trade and industry for profit in accordance with the principles of capitalism.
In the sentence
I’m a capitalist who doesn’t defend billionaires and also doesn’t feel left out…
The word capitalist is a noun.
But even if you were to pull up a dictionary definition of the word that says otherwise, in the context of the economic and political system of capitalism there’s three hundred years of writing that define capitalists under capitalism as various groups of bourgeoisie.
I think we can dispense with petty arguments over the dictionary definitions of words given what we’re discussing. If it will make you feel better I can refer to capitalists as flying purple people eaters.