The biggest issue monks have is that fights are no longer designed with them in consideration. I really became aware of this when going through the Stormblood story and getting to the Susano fight. I had just gotten Riddle of Earth, and had logically concluded that if I used it during his jump phase, around when he drops his swords, that I would be able to maintain my greased lightning. Problem is he takes so long to drop is sword that you lose it even before it drops, and the time between him dropping the second sword and him dealing party-wide damage is so long that Riddle of Earth can't be used to keep up Greased Lightning. It felt like a slap in the face to have gotten new skills to maintain my buffs only to have fights be set up to have these phases be so long as to negate their existence.

I think the main complaint monks have is that Greased Lightning management is much more demanding than it is for comparable jobs, and that our tools for doing so are inadequate for the task. I like the idea of Greased Lightning fading over time rather than all falling off at once (going from 3 stacks to 2 after 16 seconds, then to 1) And while the devs don't want to give us Greased Lightning 4 outright, if it fell off over time, a 4th stack might be able to be kept in reserve. That way longer jump cycles might still end you at 3 stacks rather than all 4, so no loss in DPS.

As far as other useless skills, people have touched on One Ilm Punch a lot, and I will say that this still is likely to never go away and never be usable considering that it's the butt of a joke in the level 52 (I think) monk quest, and changing the skill means they have to rewrite the script, something they probably don't want to put the effort into. So I've resigned myself to having that skill in my repertoire but never on my hotbar. Purification was a niche skill in Heavensward for fights like A9s that had a lot of up-time and you needed the extra TP, but now are completely useless. My thoughts there, personally, is to make the skill reflect it's name. Remove it's chakra requirement and have it mimic Selene's AOE esuna. Considering how many healers don't take esuna nowadays, this would be a pretty valuable upgrade to the skill.

Another issue is that this job is locked behind entirely too many layers of RNG. Consider the Deep Meditation trait. Apart from Bootshine, there's the RNG at play of "will this weaponskill crit?" and if that's a yes, then there's still only a 50/50 chance that you'll generate a chakra stack from it. Compare this to BRD and this is absolutely ridiculous. They get a 100% proc on their crit dots, of which they always have two up, but we only get a 50% proc rate on ours? Also as mentioned above, Brotherhood is too lackluster for any real effect. It's only physical, so if you're running a PLD who happens to be using Holy Spirit when it goes off, you're screwed, and if you have other casters, you're screwed. Also they got nothing out of it since it's only physical, and the proc rate for chakras is too low. I've been in 8-man parties with all physical DPS and still had multiple occurrences of not getting enough chakras to proc one Forbidden Chakra from the use of the skill. This needs to change. Deep Meditation needs to be 100% proc on critical weaponskills, and Brotherhood needs to be buffed to a higher proc rate (I'm not sure what's correct) as well as effect spells. As well as we need to be able to bank maybe 2 additional chakras to accommodate this.

Fists of Wind is one of the skills that I can say I only ever used when learning Sophia EX to help me get to the sides of the platforms I needed to be on. Outside of that, it's another one of those useless skills, especially as it's the weakest movement buff in the game. It's slower than Peloton, it's slower than Sprint, and it's even slower than a ninja's passive movement speed increase trait. If this is going to be a useful skill at all, I would say it should operate similar to sprint. Make it a movement speed buff on a cooldown, and maybe have it reset your shoulder tackle upon use (and combine that with the above suggestion to remove the damage from shoulder tackle to reinforce this as a movement skill)