Pros:
- Visually pleasing and fun combat
- A lot to collect, explore and do
- A lot of different classes with more added over time
- Some (read: very few) dungeons can feel really fun because of their scale/grandiosity

Cons:
- RNG gear upgrades with abysmally low rates at higher gear level
- Predatory micro-transaction shop with confusing currency conversions
- Infested by severe bot problems
- Server issues that have persisted since release that result in frequent server downtime for maintenance that is usually 3-4 hours but often becomes 8
- Mediocre story
- Most dungeons are mediocre and feel uninspired
- Pretty much everything is blocked by daily resets: mats for gear upgrades, progress for NPC relationships, obtaining rewards from certain islands and more
- Certain islands are time-gated and some even only spawn every few days. Unable to play at these times or that day? That's rough buddy. These islands also do not spawn at night so if late nights are your best time to play - that's rough buddy.
- Certain collectables are also time-gated by hiding them behind other time-gated requirements and some collectables (e.g. island tokens) are RNG to obtain.
- Argon Island exists ( an island in which you must do PRECISELY the amount of damage an ice sculpture has health and not 1 more to get a HIGH CHANCE to obtain the island soul with only 11 (yes, ELEVEN) sculptures available to ALL players on a server per day that resets 1am server time)
- Declining player base with certain content that requires groups sometimes becoming unable to be successfully completed
- No server transfer of characters
- Developers and publishers that do not listen to the player base and caters to whales far more than f2p players

Overall:
Huge time sink that enables and encourages gambling addiction and game addiction with predatory in game structures. Playing this game is like having a job except the job is taking your money whenever it catches you slipping. Can be fun for a little while due to the engaging combat mechanics. Play Lost Ark responsibly.