I think important points are that "we" probably means "Terra", possibly not all of the rest of its colonies, and certainly not all the hundreds or thousands of other cultures in Federation space (members, associates, protectorates, or not). Secondly, it may be a more recent development, as possibly contradictions may or may not apply from TOS
depending upon the interpretation of dialogue.
The point that seems to be being made is not that there are no "value allocation units" (i.e., credits
), but rather the culture and its material wealth have evolved to the point that greed has become an almost foreign concept, or at least largely an historical one. Supply has met and overcome demand in a basic sense.
Acquisition of knowledge and the usefulness to society are more fulfilling than the accumulation of digits in an electronic account or bigger and better mansions (i.e., material wealth). This does not mean that members who are more useful to society don't get additional rewards (not everyone can have a flat in Paris, for example) but these rewards are awarded on the basis of some sort of (theoretically) unbiased assessment of value to society rather than commercial competitiveness (which is somewhat arbitrary and often exaggerated).
Just as the current system would seem bizarre to a 24th Century Terran, their (fictional) system is hard to understand from today's perspective. And discussion of it in the current zeitgeist will likely generate contributions from the 20th-21st Century's Culture Wars, and their inherent confusion of freedom, democracy, and capitalism (which would be OT).