I can call my car a “flying system” all day long. Doesn’t make it an airplane.
But ideas of what is “just” change and the justice system is often slow to react. Sometimes things that are technically unjust (banning gay marriage) are allowed. Slavery was once legal. Justice system at the time said so. Also, as an anecdote, speaking as someone who has participated in the justice system quite a bit, for me it was very rarely the best determinant of what was “just” on the small scale of my life. I would hesitate to assume on the larger scale of society as a whole it is any more accurate.
The problem is that the "justice system" is the only universally agreed upon system. The alternative is everybody upholds their own justice and we have anarchy.
If you want to change the justice system, go ahead. But there's a difference between changing labour laws and going after one specific company.