I have been playing this game for a long time now, and while I can say it is very different from when the game was in it's earlier stages/seasons, it still, at least for me has that certain charm that makes the game so appealing.
Basically this game is a side-scroller, like certain MMOs, but it has 3D models, the battle system is basically keyboard based (Which for me and some people is a plus) and has a plethora of characters to choose from. I think I believe it is now at 20. Most of the characters has 4 jobs, however for at least half of the characters the jobs are just expansions of the characters initial job. The characters can be classified as MP (mana bar based, fills as you attack and only 4 skill buttons), AP (like a mana bar but has fills up on it's own and has 5 skills buttons) and AMP (Which is AP style with a mana bar). The MP characters have 4 jobs that you can switch between just by equiping a different weapon type (which is reflective off what job they are in). The AP and AMP characters only use one weapon, but their higher jobs add on to their skill tree.
Skill trees are like in any other game which when you level up you get a certain amount of points to assign certain skills, the MP characters only have a full skill tree in the first job, and the other characters skill trees basically expand when they acquire more jobs.
Speaking of characters, as of the most recent season you get 4 free character slots, with these slots you can pick any characters you want to play as. Before you had to start off with the Knight (Elesis), the Archer (Lire) the Mage (Arme) and the Pheonix (Rin), but you could unlock the others. Now You get to pick whatever 4 but to unlock more characters you got to pay for more slots, OR wait for an event where you get free character slots.
Some people get off put by the fact that there is an cash shop but its not that big of a problem. There are plenty of ways to get the highest stats without using cash at any point. Cash just helps you get them easier and has some "exclusive" stuff to them such as certain pets and armor.
In this game you can have pets that help you in battle. The free pets must be found via manuals that drop in dungeons during champion mode or during events. The cash pets while are cool, sometimes are weaker than the free pets.
There is a PVP mode, which is better now that you can customize the rules of your room. But I don't really like to play PvP that much as I am more of a dungeoner.
Only dunegons no world map that you can travel.
There is no trade system, Could be seen as bad, but It makes your items rarer (to a certain degree) and more worth while and no need to worry about losing items to people who would trade everything away.
Overall this game is a fun game, especially when you have people to play with you, The characters all have distinct styles and the gameplay is simple, yet can have depth in the moves, especially with there being advanced stuff. Even though some people say that the game is too easy now, don't let that turn you away, try it out and make the judgement yourself. This game can be charming in its own way.
(Please note that this game is made by the same people who make Elsword, which is supposedly like it's spiritual successor, and while they have somethings in common, they play very differently, at least in my opinion.)