My problem with the monk is that several of its abilities feel bad.
Like, monk feels too fragile in early levels. Giving them better AC or HP so its not as bad. They're still melee characters, not ranged.
It feels bad that Weapon Mastery doesn't apply to Unarmed Attacks. If I have a build that doesn't use weapons, its a dead feature, and puts us behind. Like, one of the benefits of Unarmed Attacks was supposed to be the option to deal damage, grapple, push or knock prone. Weapon Mastery gives all that for free now, with no loss of damage. The whole point of people asking to boost unarmed damage from d4 to d6 at start was to put monks on the same starting point as other martials in 2014. Now, with Weapon Masteries, we're behind again. You could take Tavern Brawler, but that's a feat tax and leaves W.M. as just sitting there.
Feels bad that, if I use Step of the Wind or Patient Defense, I lose half to a two-thirds of my damage output for the turn. Why not let us keep that extra attack from Martial Arts? That way, it feels less like 1 di AND -1 attack to activate them.
Everything is still short rest based. We need options for better control over short rests without messing with the timing of everything, and, no, once a day refresh at level 7 is not enough; most games end around 8-11, so that's practically end game; we need it at lower levels. Especially now that people can sacrifice a 1st level slot for more Wildshape/Channel Divinity/Bardic Inspiration, which means more people will be willing to push ahead without short rests.
It feels bad that wall running is still locked away at level 9. Doing iconic wuxia stuff so late is boring. Balancing on twigs and parkour should not be end-game abilities for a monk.
It feels bad that we're unlikely to see good monk treasures or feats. It feels bad that we feel forced to invest in ASI every time while others get excited about their new abilities.
It feels bad that, for the most part, the monk is done growing as an attacker after level 5 save for more di points and the occasional subclass.
Subclasses (other than Open Hand) actually feel good for the most part. Its really only the main class that is feels bad.