It’s a simplistic statement, but it’s not meant to be that broad, it’s meant to be taken for this type of practice.
If everyone lived off leeching off someone else or from being middlemen, without producing anything, there would only be money moved with no products, labor, or services.
It’s not meant to be applied to something like “what if everyone’s business was just opening a pub?”. The economy would be destroyed without diversification and many kinds of businesses. But being a landlord isn’t anything like that. Particularly those that won’t freaking repair anything wrong with the house, just take their checks and the tenant is on their own.
Which is why buybacks need to be illegal again, and dividends need to be regulated and taxed better baed on factors like how much the company benefits the community.
And employees need to be guaranteed a proportional cut too, ensuring that better performance and higher company earnings always means they earn more, and not that they get fired and the one who gets a bonus is some random CEO who only kept trying to push bad ideas the employees kept fighting all the time.