I don't see why trinkets weren't quickly removed along with relics. All they offer are passive stat bonuses that are always quickly mathed out in the end which gives no intuitive gameplay for the player.
I've always seen trinkets in this game as a burden rather than a fun asset. Whenever a new raid or patch comes out the first thing people look for are trinkets and find which one best suits their class and spec. If they don't do this then they get heckled by fellow guild mates or other potential guilds you are apping to. The most common situation I see was guilds asking players why they weren't taking the "DMF" trinkets because it was mathed out to be the best.
Sure we sometimes get those trinkets that provide cool aesthetics like Deathbring's Will, but soon after the cool factor just fades away and it goes back to just being a semi-passive stat bonus that we replace later on.
If we followed the same reasoning behind getting rid of relics, then trinkets should have gone with them. If we really want trinkets to stay in the game, then they need to be something that provides intuitive gameplay instead of just being a semi-passive stat bonuses that we replace every tier like we did with relics.