Currently, players dislike the current arena meta, which sees teams hold cooldowns and burst the opposing team down in 1 second, which doesn't make for engaging gameplay.
One of the new trinkets, the Cosmic Gladiator's Fastidious Resolve, is a new active trinket that grants the player 30 seconds stun and interrupt immunity on the next three spells cast at them, basically making them unstoppable for this amount of time, and in a meta where one-shots decide a game this trinket paired with this will make the game not fun for many players.
Top WoW PvP Players Against New Trinkets Coming In Patch 9.2 Eternity's End
Blizzard has been listening to the community over the last 2 patches, and many players hope they will make adjustments to this trinket or rework it entirely.
Along with the release of the PTR, Blizzard already announced reworks for many Tier Set bonuses that players have pointed out flaws on, so the same should go for this trinket.