Just about everything about how the protagonist ends up so powerful is completely unbelievable, "Ah yes, we just put balance-breaking easter eggs in this MMO because it seemed like a great idea," is... just the start of it. It never stops.
On the flip-side, if one gives it the wide suspension of disbelief it asks for, it does handle rather well the sort of laid-back and chill power fantasy that it's aiming to deliver, I think, which isn't always an easy line to tread.
Of course if you're looking for a meaningful plot, look elsewhere. There's some sense of adventure here, in a video-gamey, wander-and-do-side-quests sort of way, but no plot as such—just the protagonist becoming increasingly omnipotent and everyone acting as foils for him.
...I make it sound abysmal but I swear I've actually been enjoying it a lot XD At least in a low-effort relaxing-read sort of way. So it must be doing something right.