My first run-in with this game was in 2017, as I was looking for a game to replace Freerealms. The fantasy setting and multi-class system drew me in, as did the G1 story. Overall, it is a very well-crafted game. Though the combat system can be somewhat difficult to get the hang of at first. If you are a first-time player, I'd recommend sticking to combat, archery, or chain slash (mainly to get the required chain slash quests out of the way).
Since joining, they added in the Blaanid quest line, which can earn you thousands of levels to help catch you up. Be extremely careful with the transformation quests within the chain, as I've had the NPC for it straight-up disappear, basically rendering my character stuck/unplayable until I complete a quest way above my level.
On the subject of quests, the main ones are very good. Though there are some that definitely show how dated the game is. Be aware that the fighter quest chain is extremely annoying (all of the characters in it are insufferable and one steals 10K gold from you). Other than that, the questing experience is fun, as long as you're not accidentally doing something from G13 when your powerlevel is still suited for G1. Just in case, master windmill as quickly as possible. It got me out of some almost impossible quests.
Lastly, the community itself seems very niche. When I first joined, I was invited to a guild that welcomed me with open arms. Though the guild later disbanded for reasons I'm not sure of. After that, I made a few friendships with lone players. A majority will typically be welcoming. Though I highly suggest to keep your guard up, as I had a very scary situation happen with another player. To sum it up, maybe stick to male character models. While presenting as a female character in many games can elicit the typical responses, Mabinogi was the worst when it came to unsolicited interactions and messages from random players. Although, since rejoining earlier this year, I fortunately haven't had as many uncomfortable interactions.
Overall, I'd give the game a 4/5 for it's story, most quests, and unique talents/combat system. Though the game definitely shows it's age, and I highly suggest being careful around others in-game, especially if your avatar is feminine.