During the time of Marx, the bourgeoisie was keeping the proletariat down. They directly owned the means of production, since Soviet Russia did not have a stock market.
Now in the US, the bourgeoisie has become smaller and less influential. They no longer own the means of production due to selling shares.
Our oppressors are the aristocrats. They sit on the boards with majority power, giving direction without directly running the businesses.
Frankly, I think the Professional Managerial Class is more of an impediment to progress in the US. They're content with having 25-80% more than their peers, and thus will happily unite with the petite bourgeoisie to punch downwards at any progressive reforms.
They are, but if you're only focused on one element, without seeing the whole picture, than any solution is temporary at best.
It's not just that billionaires are bad, their existence is a symptom of a larger broken system. And within that same broken system are millions of cogs that perpetuate and solidify the system's processes. So without addressing the Professional Managerial Class and petite bourgeoisie's complicity, the system would simply create more billionaires after enough time has passed.
To say that these other elements are "a distraction" is dismissive of larger root problems. So consider that your perspective is too narrow.