Strongly agree and disagree with the bolded.
"This isn't hard to do" - 100% false. Tax law is incredibly nuanced, and you can't make assumptions about YOUR taxes and project it on NHL players. You have to be an expert on international tax law, and understand the local requirements for 32 seperate municipalities, which can have VERY different requirements. Spend 5 minutes looking on Youtube and you can identify SME's discussing tax differences that are HUGELY impactful.
"This is about fairness" - One of the secondary benefits of the CBA with the hard cap was to improve competitive balance. The goal was NEVER to achieve 100% parity. I say that because if it was, every team would be required to spend to exactly the midpoint of the cap, and every team would also have limitations spend on scouting and coaching/development staffs. The CBA understood that there were significant external impacts that impact the league, and it doesn't try to address all of those factors. Some things you can't distill down to dollars and cents. Things like general "attitude" towards certain locations due to a combination of climate, cost of living, media coverage, night life, travel requirements for geographic location, etc. Some things you can distill down to dollars and cents - front-loading contracts with signing bonuses, potential for endorsements, etc. The NHL/NHLPA put all of those into "the juice isn't worth the squeeze" bucket, and everyone knew that it was incumbent on the organizations to deal with those the best that could.
The issue we have is that some people in this thread believed what some shady people published where they intentionally and knowingly DOUBLED the impact of the no-income tax states. There is an advantage - but we're probably talking about roughly 5% in most cases. It should be noted that there are some other differences (CAN highest federal tax rate at 33% vs. 37% for the US) that never get brought up in these discussions.