Hello,
I am actually surprised by the fact that so many people consider the Champion rank something overpowered and unfair. The rank itself does not provide any in-game advantages (that Titan rank already does not have). Mystery boxes and BedWars coins are only for cosmetic purposes, experience just slightly helps you increase your level (which does not give any advantages over others as it is just a number next to your name in the chat), and map selections are just a nice quality of life improvement. The rank itself does not even have its own SkyWars kit so you cannot say it is pay to win.
As far as I can see, all other Champion rank's perks are either quality of life improvements or purely cosmetic changes. This rank is not pay to win and it does not give any unfair advantages over others (or at least it does not give more advantages than the Titan rank).