Which is not to say that it is perfect or superior to Earth and the larger Federation’s comparatively egalitarian post-scarcity economy, or even particularly ethical.
However, from what we’re shown, the Ferengi political structure (which is clearly part and parcel with it’s commercial structure) does not, with the one HUGE exception of it’s treatment of women, make use of divisive social issues to distract its work force from the disadvantages of capitalism. Unlike contemporary Western capitalism, everyone on Ferenginar from the wealthiest to the poorest appears to operate from the same transparent, if morally bankrupt, ruleset, and the powerful, importantly, don’t pretend otherwise.
This is a dark but kind of brilliant aspect of the rules of acquisition - All members of society, including laborers, are taught from birth to operate from a position of mutual distrust and can operate comfortably with full knowledge that the person on the other side of the table will disregard all other concerns in order to take complete financial advantage of them, and they will do the same. This bypasses a lot of steps that would otherwise be required in terms of building trust or engaging in any kind of sales or negotiation, although there is likely a lot more onus on each individual to do the calculus on any given business transaction internally to ensure that all of their vulnerabilities are accounted for. The phrase ‘trust me’ must be a complete joke in all contexts.
Furthermore, because greed is not just a social value but a desirable and marketable job skill, the playing field, which is horrific from the perspective of most 24th century humans, may actually be more level than even modern capitalism. There’s evidence to suggest that if even the poorest worker can successfully skim profits without leaving immediate evidence behind, this is almost blameless. Quark knows that Rom shaves the latinum, for example.
This is not a complete theory and I’m sure there are plenty of counterexamples, but mostly I just wanted to gripe that shit is so tough irl right now that even working as a Ferengi waiter seems like a dream by comparison.
Honestly, your “the most stable and ethical expression of capitalism” thesis has made me realize just how right Quark was. With humanity, the wealth gained through unchecked capitalism inevitably gets parleyed into political power that destroys the free market that enabled it in the first place. For Ferengi society to be stable, that dictatorial tendency would have to be absent, which means they really are better.