Quark is a businessman and he has employees. The basic idea has been that Ferengi are a bunch of privateers, not people who are docile enough to work in gigantic bureaucratic structures.
The part of the Ferengi government we see, the Grand Nagus, is as capitalist as it gets. Note that colonizing has often been done by governments. Take a look at what the Chinese are currently doing in Africa, that's only possible with a strong autocratic government (which is basically the same as a large corporation). Hard to picture Ferengi being engaged in such activity.
Quark's business is a sole proprietorship, not a corporation.
Also I think if the Ferengi were supposed to be a commentary about capitalism run amok (specifically American capitalism) the Ferengi should have had corporations. In their first appearance they seemed like a generic warrior culture, rather then business men.
Also I don't think that just because Ferengi society is about acquiring profit, that doesn't mean every Ferengi is suited to be business leaders, its the reason why Quark ran the bar, while Rom was just his subordinate, because Quark had a more forceful personality and better business skills, despite the fact Rom had better technical skills then Quark. I do think some Ferengi would be docile enough to work in a corporation rather then everyone in their society trying to be an entrepreneur.
I think one of the problems Ferengi as villains is they had no patience and a desire for instant gratification, almost none of them seemed like more sinister, subtle long term planners. So yeah written like that, they can't create corporations, but they also don't work as effective villains either. Lex Luthor is driven by greed and ego, but he comes off as a rather subtle, long term schemer.