OP Legacy Uniques are the worst decision i've seen from the devs thus far

Optimal for what exactly: for survival of the individual, or for survival of the community/society/species? The case you're alluding to is the typical Prisoner's dilemma, in which the action deemed immediately optimal for the involved individuals returns suboptimal results for all of them. The optimal decision is for all involved parties either to cooperate and have trust in each other, or never let any of themselves enter the dilemma in the first place. Which I'm quite sure you know, not being the humblest person when presented an opportunity to boast superior intelligence.

You must also understand that it is more of a mentality issue than it is the issue with Marxism, communism, or any other modern ideology that hasn't truly succeeded in practice, per se. Until the critical mass of individuals who comprise society sufficiently understands why it would be better for anyone, including each and every one of themselves, to be cooperative and deny the importance of surplus personal wealth (i.e. strive for securing long-term well-being rather than the immediate), any ideology will fail—even the most conservative, even the most liberal. Communism in Soviet Russia failed largely because people were visibly denied the security of both immediate and long-term well-being while they saw high-ranking bureaucrats prosper personally. In early twentieth century the perspective was a lot more promising as a whole.

With regards to legacy vs. global nerfs in particular, this isn't too much different: purposefully allowing the few to have a significant surplus further disrupts economy for everyone and creates more problems than it solves.