You're not supposed to cap them, you're supposed to gain them till you get the important subjob benefits and then let it happen naturally from doing events.
Stop Mlevel grinding to cap like machines, you're missing the point.
The point is so you can have a progression system you gain naturally while doing stuff, it's not fun to cap out your favorite jobs. It's a sub-concious thing that makes the game more fun to progression junkies. I did a few events yesterday, and it felt good at the end of the day to get that +1 mlev.
Being too goal orientated gets you to the point you have nothing left to do, given the nature of XI in 2024 that's not a good idea.
Black Desert has a similar system, except there is no known cap there and nobody tries to reach it cause it's insanely hard to gain levels beyond the soft cap. XI players are a different breed though.
I hope they never add any +mlev items, campaigns or rings, cause they will be sending the completely wrong message to the players.