I agree with you!
But, until the day comes when players stop looking for that magical one number which encapsulates a player's performance, parsers will remain a divisive topic amongst the FFXIV community.
Here's the thing. Not everyone is concerned with being as efficient as possible. A lot of players play FFXIV for fun.
Meanwhile, you have another group who desire to be the best they can be. They want to get through the content as fast as possible in order to play the game at its highest difficulty.
I like to call this the Casuals versus the Hardcore debate. Now, parsers are fine for players who are pushing difficult content. Players need to be in their top form in order to overcome the challenges placed in front of them by the developers.
However, what happens is when the hardcore players encounter casual players going through dungeons to complete quests, parsers become this weapon to use against the casuals and it ruins the casual's enjoyment of the game.
Boiled down, FFXIV was not designed to be a competitive game. It's a story driven MMORPG. Parsers don't comfortably fit the audience.