Short:
The game is designed very very specifically to get you locked into its compulsion loops through FOMO. Smilegate likely hires more behavioral scientists than it does game developers. I'd wager that the only reason most veteran players still play are because they are either stuck in the loop, or because of the sunken cost of how much they've already spent on the game. All progression in the game is time gated so as to promote spending to bypass these gates.
Combat and SOME raid design is the only good thing about this game. Everything else, the compulsion loop, a lot of QOL, class balance, story delivery, launch time (it's 2024), etc. are absolute trash.
It seems counterintuitive to give a bad review for a game I put in 9.4k hours on, but that is the power of the FOMO compulsion loop.
Long:
Pre-launch (day 2) veteran player that played at the top edge of the end game through every content release from Argos to Thaemine HM and would be ready for the next two content releases (Behemoth & Echidna). 300 roster level "F2P" ($100 total) success story with a juiced main (1633, all 10s, +25 Akkan weapon, 9/7 stone, 40 elixir) and an accompanying roster of seven adequately geared 1600-1610 DPS chars.
Game optimization is reaaaalllllyyy bad. As an old game running on Unreal Engine 3, it is likely a monstrosity of spaghetti code at this point. It takes forever to launch and is just horribly optimized.
The overall story of Lost Ark is decent, with a portion of players considering it to be really good. However, try to ask most veteran players what this story is, and they wouldn't be able to tell you for two reasons. First, the compulsion loop and time gating promotes getting your "homework" done as fast as possible. This leaves little time to try and enjoy the story, which for some parts (even with Shift+G skipping) can take hours. Second, the delivery of this story is atrocious. Random clips, (overly) dramatic pauses, forced "roleplay" (sit here 10 seconds while your char talks to NPC), and many other issues make actually trying to go through the story a huge bore.
This rush to get homework done also makes the community really bad for new players. This will never be truly changed because they want players to FOMO and pay to bypass time gating.
The GUI is horrible at saving window positions. Certain things, like trying to hit tripods are just poorly designed so that the two buttons you need to press for an attempt are offset just enough to leave only a fraction of a millimeter to click both buttons without having to move your mouse.
Everything is RNG. How strong you are, and if you spend money, how much you need to spend, is entirely dependent on RNG. Random gold income such as accessory drops, fate embers, or sidereal energies (some people getting multiples) completely change the player experience. Every single system to increase character strength is RNG, such as gear quality, honing gear, cutting rocks, elixirs, transcendence, combining gems, with some of these systems having multiple layers of RNG.
Combat and raid design (difficulty) are the only good thing about this game, but even these two areas have issues.
Combat is fun in that it's mostly fast paced and reactive. It feels good to play a character and use your skills during encounters to try and maximize your damage output. Many classes are designed well with their skill rotation so that this is just fun and probably one of the better designed combat systems.
However, the issue is with how that design fares in raid design or even PVP (GVG). Classes have evolved over time because the raid design has evolved. This raid design has hit snags MANY times and ultimately, much of the difficulty is more annoyance than actual difficulty (attacks hidden behind the boss, screen/background color closely resembling attack colors). Since all enemy attack rotations are completely randomized, there are a lot of instances in raids where bosses can overlap dangerous skills, or sit up against a wall where positional attacks are restricted (and some skills become infinitely more dangerous). Also, some encounters have been designed well in which attacks that can be countered will ignore the internal cooldown, but many are just spaghetti in how this ICD is approached, which honestly shouldn't exist at all for a skill check that can (due to random enemy rotations) happen multiple times within the ICD.
Smilegate is also just absolutely horrible at how long it takes to balance its classes or the game in general, and with how they're balanced. Many classes have been in need of a rework for upwards of a year or more. It's also pretty well known that every new class is purposely overtuned to attract players before it's "balanced" back down after all the FOMO spending to build up that character. For example, the problem with the entropy (back attack) set still doesn't have a solution on the horizon, and I'd wager whatever they eventually implement will suck.
Also, most people don't care about this, but the recent S-tier GVG island changes are also just, to put it bluntly, retarded.
Although AGS has its hands tied in many regards, it also sucks at fixing many of the issues that it can push for. Win trading in PVP Arena (submitting video proof = witch hunt/bullying), teaming on Primal, chaos botting, and although cracking down recently, combating RMT are just some examples.
I would not recommend this game to anybody. It's designed to feed on your addiction and actively promotes FOMO which leads to toxic behavior.