Sure, I'll go in order of leveling.
Fists of Earth, Fists of Wind, and Fists of Fire as well as the traits enhanced Fists of Fire and Riddle of Wind: They're currently designed and with every iteration of the traits they've attached to them, has only ever had one stance you want to be using for the vast majority of the time. Up until level 76 that's fire because it gives you more damage, and at level 76 it's Wind, because GL4 gives you more damage. The entire system is superfluous and could be removed right now, or turned into traits, and nothing would change. They're not just wastes of buttons, they're wastes of buttons that continue to get new traits that are also wastes of traits which bars any sort of progression of the job along that vector.
Dragon Kick/Leaden Fist: Creates a disproportionate amount of potency on a single Positional (missing that positional alone is nearly as much as missing every positional a Dragoon would hit in both of its combos). It further incentivizes Perfect Balance to be used as a DPS cooldown to spam Leaden Bootshines when the developers clearly want Perfect Balance to instead be our "Build up GL and other buffs" button. A better way to alter Dragon Kick going into Shadowbringers would have been to make it a persistent self buff to Critical Hit rate or even just as a flat damage buff, that is what it it functionally was when its effect was inflicting the Blunt Resistance debuff since no other job used Blunt Damage anyway.
Meditation/Deep Meditation I and II: While Meditation as it was designed in Heavensward was fine as our pseudo ranged attack that we'd use on short disengages, Deep Meditation I and II both are at odds with that design and Monks design as a consistent damage dealer as a whole. The RNG nature of Chakra gain and the gauge only being useable when its full has several problems. The biggest one is a problem of feel compared to Monks identity, the job should be about consistent output, but RNG is at complete odds with that. Mechanically, by having no control over Chakra generation we can and will enter disengages or down phases where we'd want to build Chakra but will be less able to because of existing gauge. Because it's based on crits, this also emphasizes something the devs have tried to get away from by making Monk composition dependent on Dragoon, Scholar, and Dancer for their critical hit buffs. The gauge being all or nothing also means that it's common and unavoidable for overflow to occur and for gauge to be lost during Brotherhood windows. In general, people don't like the RNG on this job and our gauge should build in a more consistent manner such as by executing Coeurl form skills.
Tornado Kick: The reasons for disliking this have been well recorded, for all that it has great visual and sound design, we're basically dis-incentivized from using it at any opportunity because the rest of our kit is built around keeping Greased Lightning up. This skill is a newbie trap because its high potency and flashy animation will make people want to hit it. In actually it's currently only useful for excessively long phase changes, or executes. However, because it's also a sizeable amount of burst if we can recover stacks easily and the devs don't want us to use it as such, it's also the noose around the kits neck that caused them to nerf Perfect Balance back into oblivion. This skill more than any others needs a different effect.
Riddle of Earth: As designed in Stormblood it was one of the stupidest possible skills for a DPS to have. It was extremely unreliable for proccing because you could enter a phase where you would need to be hit at varying parts in your rotation depending on how consistent your play was, which could result in GL falling off before it procced. It could also be blocked by a Scholar shielding hard enough so sometimes it just wouldn't work anyway. Now it's a 30 second True North effect with the same ridiculous activation requirements. It's a little better now, but Monk's identity is partially tied to maximizing your damage through positionals, and being able to ignore that for considerable periods with this is an overblown choice.
Brotherhood: It's problems are tied into the previously mentioned Chakra problems and RNG, but also party composition. This skill only gives you chakra procs from physical party members and it's balanced around an 8-man party with one caster DPS. Anything outside of that general composition feels terrible. So solo duties, 4-man dungeons, or any 8-man content you run with a roulette which could give you a party full of casters is more than likely going to whiff and maybe get one Forbidden Chakra if any. However it also doesn't work in an optimal party composition either, because it can still whiff if the RNG is bad. Meanwhile, if the RNG is good... it still feels bad, because the all or nothing nature of Chakra means there's going to be overflow and lost procs. The skill is never satisfying to use and incredibly sensitive to party composition messing with it.
Enlightenment: While conceptually fine, this is a skill we should have gained at level 58 or so when we gain access to our gauge. It is not a Shadowbringers skill by any stretch of the imagination, we just get it there, it's a Stormblood skill the expansion where their selling point was every job having a Gauge. However there was no effort put into Monk in Stormblood or Shadowbringers for that matter, so we get it later than we should. This means it has all of the problems of Chakras, but earned far too late at such a time that it feels like a worse replacement for a skill they just removed which should have been an actual addition in the previous expansion instead of something to be excited about.
Anatman: This skill should not exist, full stop. It was designed to yet another Greased Lightning Upkeep skill with some major flaw that will render it nonfunctional in situations (In its cases, any time you have to Move) as well as an inefficient means of recovering stacks after they nerfed PB's cooldown. Right now, with Form Shift does the upkeep function in significantly more situations. The building stacks function I'd posit is intentionally ineffective, because if it was useful, then we'd use it for Tornado Kicking and god forbid we have buttons to hit, but as a result of it being ineffective the situations where it's useful are few and far between. However as far as unintended uses go, this also is the crux of the terrible feeling anatman opener where you fish for a stack of Greased Lightning so you can dump out Leaden Bootshines using Perfect Balance, which is one of the worst feeling things the game has ever had.
Six Sided Star: Yet another yet another skill for refreshing Greased Lightning, this time on disconnects. This has the most niche uses of any skill we have, that being short disconnects. However it inherently is at odds with Meditation for that duty, the Greased Lightning refresh function is redundant with multiple other skills in the kit and Form Shift just does it the most effectively right now, and really it's just... extremely disappointing as a capstone skill. It's visual impressive like Tornado Kick but about as useful in general.
tl;dr: The gauge is poorly conceived RNG that Monk players actively don't want, lackadaisically attached to a different mechanic in such a manner that makes both less effective and enjoyable. Brotherhood and Crit RNG mechanics makes the job composition dependent even though basically no one likes that, and that its something devs have tried to avoid this expansion. We have dozens of skills competing to do the exact same thing in our kit making all of them less effective, and more skills that straight up could be deleted right now and change nothing about how the job plays because they're pointless and poorly conceived. Despite all of this, we're doing less than what we would in the ARR rotation because they've trimmed skills from the job.