Because (and again personal opinion) there is a significant difference between being rewarded for being skilled at game mechanics, such as PvP, in contrast to rewards provided by RNG.
Some of the PvP islands grant the island soul through sheer grinding. No one can really complain about these. You’ll get the rewards you seek, it may simply take a little while longer, but you can measure your progression.
Other PvP islands are RNG, but this RNG can be boosted by opening island chests (Illusion Island and Lush Reed).
I argue that collecting souls is far more valuable to all players, in comparison to the cosmetic rewards available in PvP proving grounds.
Souls grant access to sailing compasses, Stronghold statues, and masterpieces. Most players would consider these items valuable to aid in both horizontal and vertical game progression.
Now there is an argument that under RNG, anyone could get any reward at any time simply by taking part - yes, you’re not wrong. Now. Imagine you are not very skilled at PvP or simply don’t enjoy the PvP experience so you are prone to dying. Imagine you’ve visited Illusion isle for the 50th time desperate to get the island soul.
The OP of this thread has provided feedback, as is their right, that phoenix feathers are the issue. I argue that is not the case. The presence of chests and the RNG buff they provide is the real reason why these islands create a love or hate community relationship and drive the “toxic” behaviour the OP observed with feathers, again, assuming this behavior is only to troll. To some players, respawning next to chests and denying others the opportunity to open a chest is perhaps the only way they will ever have a chance to get access to this content themselves.
Is the ultimate argument, hey, just remove RNG. Perhaps. But at least Pheonix Feathers (which aren’t cheap by the way) provide a slightly level playing field regardless of skill.