The fact is, combat in Mabinogi is expensive (both gold and time and RL money wise), imbalanced, and compared to newer games on stronger engines, both difficult and frustrating and unengaging for most people. Who has time to grind stats for a year just to be relevant? Who has the patience to do multiple grindy life skills just to get past content that was obsolete 4 years ago?
Yes it has a certain niche appeal, but the fact is, only 1% of players per server will ever do the high end content, maybe 10% of the players are even strong enough to do Adv/ Hard Mode no modifier Alban, and let's not even talk about Rabbie Phantasm. Meanwhile, a nifty music system update brings several hundred people plus back in a weekend. Why? Because the average player can actually access this content, it's fun, it brings people together in a social manner. And it has its own limitations, sure, the hype will die down a bit, but the fact is, Mabinogi is a social game, the directors who tried to push it in a more combat oriented direction made a big mistake, and that's what the game should emphasize.
Rabbie Phantasm? Who the fuck cares. Unless you have Korean work ethic or have been playing for a decade you're never going to have the stats for it. Most people don't have the time or inclination to train, and the people who do aren't going to hardcore minmax. How many people even took advantage of the summer daily RBs and training events? Not enough, for sure. And even if you can run it, who wants to speedrun the same dungeon over and over again for a 1% chance of an enchant that boosts your dmg output by 1%? Only a small subset of people.
The way to revive Mabi is more updates like Music Q that focus on the social aspect of the game, and emphasize the fashion aspects of the game that aren't as NX based, as well as making life skills more rewarding. DevCat should just accept that combat is not the game's strong suit, and focus on releasing more content for people who want to have fun, make friends and explore.