Speaking of sniff checks, you might want to do that first, because that's not actually the prediction that Marx was making.
In my understanding, Marx was actually appreciative of free market building stuff. The question he asked was this: If the workers pay for the goods produced with increasingly bigger share of private property of capitalist class, what happens once there is no more property to give away to capitalists? (And he was actually the first to ask this question, and treat capitalism as a dynamical system, which makes him into one of the greatest economists of all time.)
Of course, it didn't fail completely, for two reasons. One is people actually instituted social democratic and keynesian reforms that prevented the collapse. (Marx was an optimist in that people will learn and eventually reject capital ownership completely, but they didn't.)
The other reason is that we continuously invent new forms capital (private property) to inject into flailing capitalism. In other words, we find more and more public goods that can be privatized - things such as mortgages and other consumer debt, intellectual property, new financial instruments, health care insurance, private and behavioral personal information ("big data"), new forms of money such as Bitcoin, openly available information sucked up by generative AI etc.
But that doesn't mean capitalism (especially its financial arm) isn't parasitic - it just didn't manage to kill the host yet.