I’ve played manye games in my life, consoles and pc, and theres something always i like: Events, not that kind of seasons like D3 or PoE, but seasonal events, like for example Summer, Christmas, Halloween, etc, and also Permanent events, im gonna give some examples of this events:
Christmas: Mobs has a chance to drop Santa Box, the santa box has a chance to drop a special skin sword (like a candy cane) with normal or better stats doesnt matter, or other items like candies to get some buffs, you know what i mean, alot of games used to do this.
Every map has a chance to spawn a “Big Version” of a mob, not a boss, this big version gives more exp, and a chance to double coins, for example, and a chance to drop a special weapon with other stats, i know theres a “Wealth mod” in PoE, but something different, ill think on a better example.
Events by time, special maps with special coins to exchange but with a Schedule, if you know MU online you will understand, this would be good to farm Set Items, also you can apply this to pvp or arena system.
Ill try to give more ideas, but i guess this will add some “life” to the game, i know its kinda classic but if we focus only on lvl and builds, it will turn into something like PoE, finish the season in a couple of weeks, get the rewards and go play something else or try another build.