Aside from being a game filled with hazardous paywalls (which can be easily averted), and other nasties with the ingame economy, I really don't see why this title gets so much flak from the community.
Solid Multiplayer RPG, four man dungeon crawling. Wearing armor and items while you complete levels allows you to gain EXP (Known as Heat) to further level the items to a maximum of level 10. From there you can transmute and pick different branches that you want to evolve your weapon for a cost of in-game currency.
The game used to employ a revive system where you would share your HP to revive them, and uses now items known as Spark of Life. The game used to be much more limited in terms of how much you could play per day, your Knight would store "Mist Energy" in their armor as time passes, and you could use this energy to power the Elevators (which help you advance to lower dungeons in the specific dungeon series).
The dungeons in general are randomly generated based on user contributions to that specific elevator, by adding different crystals (which you can find in almost every level), you may influence how the next dungeon will be generated. I believe it is a nice addition to the randomness of the stages, and it forces you to be prepared for the dungeons you go into.
The netcode is rather solid, I have not had many problems with my connection and playing the game, aside from the occasional lag spike between other players.
The themes and atmosphere are well designed, and the music compliments said environments.
All in all I would very much reccomend this game to my friends and family, even though my opinion may be unpopular.