First things first, Mabinogi 2 has been cancelled for the time being. It was to be a separate game that is kind of like a Vindi/Mabi Hybrid (if I recall correctly)
Mabinogi is popular for quite a few reasons. It has a classes system for one, you pick a skill set to "specialize" in on character creation/Rebirth, but that only makes you rank up skills that fall under that category faster and it affects your stat growth upon leveling up, which isn't a big deal.
Each week you can rebirth, rebirthing brings you down to level 1 again, but you retain all skill levels and all stats gained from ranking a skill (ie, you gain 30 Strength from having Rank 1 Smash, you rebirth, you keep that 30 Strength)
The game is worth starting, newbies can rebirth every single day until Total Level 1000. That's enough to master a skill set (save a few extremely costly ones, like Magic and Guns) You can also reset your skills for free before Total 1000 so you can experiment as much as you'd like. (Be warned, it adds up your Normal Levels, and Exploration Levels when calculating the Total 1000. The latter is gained through exploring the other continent)
But anyway, there is a ton of stuff to do in Mabi that is not combat based. You can make a character that never picks up a weapon and crafts or plays music. You can level off of the commerce system by bringing goods from one city to another.
Keep in mind the combat is twitch based, you need to click to attack, and certain skills counter other ones. For example, Defense>Normal Attack. You'll stop and be open for an attack, but Smash>Defense, on the other hand Smash loses to Counterattack, etc etc.
Its worth a shot, just don't be one of those grouchy players that hates on the people that have played for 3+years and have everything maxed :P no one likes those players.