Please don't just talk the talk, but actually walk the talk, Square Enix: If you want this game to have longevity, you need to fix ARR. Because players will eventually quit the game and you need fresh blood to replace it. And if they play through ARR, a lot of them will be extremely unimpressed. FF14 is drifting on the tailwinds of its success from Shadowbringers and, probably in the near future, Endwalker. It is also benefitting from the dearth of decent MMOs out there. I'm willing to bet this game's recent success owes in large part to the failure of other MMOs to produce good content, especially in WoW, not because FF14 did anything much better, other than the story. Longevity of an MMO will never be derived from being the least worst option in the genre. With new MMOs with budgets on the horizon such as New World and Ashes of Creation, along with a billion ex-Blizzard indie MMO projects, now cannot be the time for Square Enix to drop its vigilance.
While there are many other issues with the game, the biggest issue right now is that, frankly, ARR sucks. Not just when compared to Shadowbringers, but in a vacuum it still sucks. The quest abridgement did nothing. Half the quests in ARR are still boring fillers with no meat to them, with the pace only picking up in 2.4-2.5 and Lv42-50. While there's not much that Square Enix can do without rewriting the story, they have not gone far enough to remove the bloat that no one cares about and does not pay off in the future.
With the skill gutting that comes with each expansion, the leveling experience below Lv 50 is also horribly boring now. On many jobs, such as Dragoon, healers, and so on, you only get one AoE ability. One. Even a player completely new to MMOs will be quickly bored by their sparse toolkit at Lv50, particularly since there are more than a dozen dungeons, eight trials, and quite a few raids that they have access to at Lv50. Veteran MMO players will likely doze off before they even reach Heavensward. The story alone is not enough to carry the leveling experience, Square Enix. This game is a Final Fantasy before an MMO, but previous Final Fantasy's have also iterated on gameplay to keep things fresh. You need to look at the gameplay below Lv50. It's in an atrocious state right now.
There is also next to no challenge or thought required in the ARR endgame. Because of job changes and a huge ton of item level advantages, you're skipping mechanics left and right in the Lv 50 dungeons. This isn't unique to the ARR endgame - it's also an issue with Lv 60 and Lv 70 content. But unlike the HW and SB endgame, truthfully the dungeons and raids cannot be carried by the beautiful aesthetics and soundtracks of the later endgames. Tam-Tara Hard Mode still looks dull and murky, no matter how many fresh coats of paint you apply on it. It cannot compare to say, the beautiful sky islands of Neverreap or the much more intricate designs of the Skallic ruins. So it's all the more urgent that Square Enix make sure that players get to see the creativity in the mechanics of Lv 50 content instead of just skipping them through sheer brute force of overgearing. While the stat squish will no doubt help somewhat, they need to manually tweak the content so that playing them synced feels like playing Lv 80 content synced right now. Either impose a lower item level sync in Lv 50 content or buff the HP of bosses. I want to see players having to figure out what to do with the Zu eggs in Pharos Sirius, not just have players brute force through the fight and winning anyways because everyone's HP and damage is too high for the content.
There are many more issues with ARR but these are the biggest culprits - bland story, boring gameplay, and content that does not require any thinking due to overgearing. It is imperative for Square Enix to fix these issues with a permanent approach, so that new players will come to this game and not be bored with ARR and leave - I've known many such players.