Eq2 uses an xp slider. Turn it to 100 % and you level at maximum xp gain rate. Reduce it to 50% and you level 50% slower. Set it to zero and your character won’t level at all. Blizzard should at least do this. Give players ability to. Choose how fast they level.
I should also mention eq2 has concept of xp vials. You can redirect a portion of gained xp into a vial and pas a filled vial to an alt to help em level up fast.
Not saying these systems are perfect but they do give players choices