Monk has been struggling ever since around patch 2.4 if we're being honest.

The power of trick attack and emnity management on the job was incredibly strong not to mention its ability to raise tank damage by increasing the damage bosses take from slashing damage types (something not removed from the game until Shadowbringers) The addition of dark knight in heavensward really didn't help this either since monk's previous party utility of making bosses deal less magic damage was made redundant when that ability was added to a tank's toolkit.

Monk saw a few bursts of increased player interest between then and its rework in Shadowbringers, but between then every time the job got something interesting, the devs considered it an oversight and patched the job to remove those playstyles. (tornado kick/wind tackle monk in stormblood is a good example of this)

Based on what I'm seeing from their recent patch notes, I question if anyone on the development team actually plays the job since they had said that with Dawntrail the addition of fury stack wouldn't change the job's rotation, which is incorrect. (twin snakes for 5 expansions was always used every other rotation and demolish every third where now twin snakes is used every third rotation and demolish every fourth)

A lot of what's hurting the job at this point is that its playstyle hasn't attracted a lot of new players while also removing the aspects of the job that long-time monk mains loved.