Monk and Black Mage are 2 classes that, up until EW, shared the same common problem, and it's around this bit right here.
Nothing was dreadfully wrong with either of them, both have (had) been wallowing in stagnation for expansion after expansion because they were both being held back by mechanics that made them unapproachably difficult for the 'average' player to play.
In BLM's case, it's the AF/UI timers, which make the class so difficult to understand I still, to this day, see people chain casting fire 3 because they don't know better and can't understand the rotation, because the class has no structure, at all.
In Monk's case, it was around 2 things. Positionals, kind of, and Greased Lightning. GL was hyper-punishment on top of already pretty badly failing to play the class correctly. Get rid of that and the classes popularity already saw a jump. Positionals are a love-it or leave-it mechanic.
For a significant chunk of players, positionals are the single biggest reason we don't touch melee DPS classes. Actually, it's the least interesting aspect of any and every melee DPS class. If every melee DPS with positionals had them removed, the game would be a fair bit better off for it.
But the important thing is understanding that you don't just remove something in a vacuum. You can't "just" remove greased lightning or "just" remove positionals. Something needs to take its place. Which Masterful Blitz did. The first time Monk has had anything vaguely approaching a real identity was when they added masterful blitz to the class. Before that it was a fast positional masher with about 20 more oGCDs than it needed. For once, the class has its identity and for once, the class has seen an actual change for the first time since ARR came out that breathes fresh life and popularity into the class. And for the first time since Stormblood came out and ruined Ninja (for me), I can say there's a melee DPS I would pick as my primary. And I hate literally every aspect of Monk's thematics except its actual gameplay, so that says a lot when I say Monk is the only melee DPS I like right now.