PvE design:
Encounter design - improving, albeit very slowly. The Alagia alliance raid has shown they were willing to experiment with arena layout in the enemy encounters. This is a good thing. The bad thing is that encounters are still so mechanically heavy that it barely tickles once you understand the mechanic correctly (but this is also partly due to high ILVL gear sync when this raid was released).
Class design - It's improving in some ways but getting worse in others.
For example, having skills like Macrocosmos on AST and Expedient on SCH is starting to really give a unique identity to the way certain healers should function. However, healers are also too bloated with healing abilities that they functionally still play the same for any content (you constantly press your single target attack button for 90% of the time and weave in one of the 20+ healing abilities in your toolkit between the 1.5 second cast and 2.5 second recast cooldown). This is very bad because... healers don't actually feel very unique when damage isn't enough to justify the use of these skills. This happens when players get better at mechanics that they don't take as much damage + when healers get into a solo instance and the instance's damage output is so low because it's designed for what a DPS can handle, so you get the feeling of just spending even more time pressing the same attack button that you always do in all content even more. Thus, healers can feel like a carbon copy of each other because they all spend their time pressing the same skill they unlock at level 1 without much variation from level 4 to 90.
For DPS in particular - some jobs have been suffering and other jobs have been improving. In particular, the change on Samurai's Kaiten takes away some identity and leaves a gaping hole in the feel of the job, as well as the skill ceiling (something players strive for when playing a job and keeps them interested in the job). The same goes for Summoner because it feels like they play the exact same from level 50 to level 90 with barely any difference. The good (and also bad) news is that there is some changes meant to make the job feel better to play at lower levels by introducing certain job skills much earlier (SMN's aethercharge -> Dreadwyrm Trance + the three crystals, Ninja's Assassinate -> Dream within a Dream). The bad news with these changes is that because they were added earlier on, the amount of skills and gameplay later on seems to be lacking because it doesn't feel like the job evolved much because you're still pressing the same buttons without any new form of interactivity.
For tanks... you can directly exclude a healer once you are familiar enough with the mechanics in most content. You can keep yourself alive and the party alive. In some ways, this makes a healer feel like an extra or a gimped DPS when everyone knows what to do.
PvP Design:
The best I've seen in ages. All jobs are now unique and fits into their intended job fantasy. Team composition will actually matter because each team with different jobs have different strengths and weaknesses. The key to winning is to take advantage and play to their strengths while reducing your weaknesses that the opposing team can exploit.
Healers feel unique, which is a breath of fresh air to the role. They are not so overpowered to the point that they can just undo any mistake a player makes on their team. Mistakes are properly punished - and this is one thing that makes PvP good because you're fighting against real players. You do not feel invalidated just because a healer exists, nor do you feel a healer is essential. Healers are simply just part of the game mode rather than an exception (compared to PvE in where you can just directly no longer need a healer since your tank can just heal themselves).
The design of Recuperation, Purify, Guard, and Elixir allows a lot of flexibility in job design because every job has the required tools to guarantee their own survival, but not overpowered because all jobs have their own way to circumvent them. It opens the way for a lot more tactics and strategies to happen.
Overall the balance is mostly positive. There has been checks to ensuring the balance is kept well in PvP without taking away of the fun of a job. I hope they just don't look specifically at winrates since a large portion of PvP is highly dependent on player skill too. Black mage is the most notable example - overtuned this patch (6.11a) but will be reverted and readjusted soon. Other than that, PvP is pretty solid and can be almost mainstay content. Especially for players who prefer a faster action-paced gameplay akin to a MOBA.
The most pressing[?] issues with PvP is
1. Server tick. Sometimes Purify or guard doesn't register as fast as it should before the next server tick. The good players take this into account and pre-emptively guard & purify as well, but sometimes it can still be an issue.
2. Rewards. Season rewards doesn't seem very interesting or unique after the attaining a tier beyond the first time (Ranked Tier Border for Portrait + # Trophy Crystals). This might not be a high incentive to continue playing PvP since you gain nothing out of it. All items in the trophy crystal store are one-time unlocks, which can prove to be an issue down the line when you have more trophy crystals but nothing remaining to buy.
Housing:
It was doing bad. Now, housing is doing better. Lottery system now works. Overall, upward trend. Still a problem for a lack of plots FC vs. individual player housing though, but at least it's not as bad as having the whole lottery system breaking down.
Graphic Design:
Doing well still. We still got amazing glamours and cool dungeon/raid graphics. The number has dropped considerably but the quality can be argued to be a lot higher. We also got a glamour dresser expansion coming soon (400 -> 800).
... Well... graphics are doing well overall, except for..
Character Customization:
Let's be honest here... Hrothgars and Vieras don't get all the new headgear moving forward, which puts them consistently at a weird place since it's no longer 'the issue of not having enough time to fix old headpieces'. The problem gets worse with Hrothgars being promised on new hairstyles for years without being shown any indication other than a promise they were being worked on. Then 2-3 years later, the implementation looked like a very low-effort result and thrown together at the very last minute for 3 hairstyles in total. Then, Hrothgars are being told they will have to wait even longer to get new hairstyles because they didn't want their ears to be hidden in a hairstyle. Hrothgars have to now wait more than an expansion's worth of time just so... they don't lose out on another character customization slot (earrings)? The dismissal of the race's concern felt really bad to me and many other players. That's just a huge red flag to me that this race wasn't given proper care at all.
Other than that, all the other races have been getting more hairstyle support consistently throughout the expansions, which directly contrasts the expectation further. We do know that character models will get a graphics update - which is something players can look forward to.
... Though they haven't shown Hrothgar or Viera when they shown character models in the liveletter during that demonstration. Now, normally I'd just leave it at that and we can be expecting to see Hrothgar/Viera later, but now that there has been a consistent and VERY noticeable contrast between how Hrothgar/Viera are treated with the other races, it's just something to consider... Will they get proper support? Or is this just an empty promise again? The damage to the trust has been done. Only time will tell.
tl;dr - They're working on improving the game, but they ended up neglecting other parts of the game as a result. And the neglected parts have been getting worse instead of being fully addressed, which drags the whole game down like a festering wound.