Theoretically I'd love to work at an environment where you're paid fairly without having to negotiate, and where negotiation skills would not affect one's compensation. However, wherever productivity is hard to objectively quantify (which is very often the case), the compensation is unfair out of statistical necessity (errors in attempts to quantify productivity are much more likely than no errors.) Negotiation skills will thus necessarily impact compensation because they're basically about convincing that you're worth more than you're paid and employers cannot be "immune to convincing" because they have no truly objective criterion to rely on.

Another angle is that there are many things worth working on in environments where fairness is not only an elusive goal, but not even something the employer aims at; rather, they aim at minimizing their expenses, or out-negotiating you for the sport of it, etc. You can stay around for a while, underpaid, and then quit and not work on that thing anymore; or you can negotiate a better deal and stay and keep working on that thing. Sometimes you might prefer the latter. Another scenario is, your skills are uniquely valuable to someone who minimizes expenses rather than maximizing fairness, and the best deal you are likely to get for yourself is by negotiating with that party.