McMMO is literally the worst plugin ever in my opinion. It rewards grinding and farming and severely punishes newer players:
Oh, you've only played on here for a week? TOO BAD. I'VE BEEN AROUND FOR 3 WEEKS. I HAVE CHOPPED DOWN MANY A TREE, AND MY STONE AXE SHALL VANQUISH YOU IN ONE SWING. I AM XX_SUPERPROBRO_XX, CHOPPER OF OAKS AND PUNCHER OF PIGS.
I like the idea of leveling up and having a long-term goal, but McMMO just does it horribly. I think a game should discourage grinding, farming, and otherwise not playing the game the way it's intended to be played. "Let's make a game where the player goes AFK for 5 hours then spam-clicks a bunch of monsters, then repeats!" said no game designer ever. Players should be encouraged to do amazing and incredible things, like fighting an enderdragon or exploring a mineshaft. You can literally reach the maximum combat levels in McMMO without killing a single hostile mob.
If you want to make a survival server interesting, I've found that adding custom gear/items/mobs does that job very well and very simply. Minecraft has tons of unused features like potion effects, mobs, item attributes, and enchantments that can be added fairly easily. This gives us the ability to make several different types of gear. Rather than having diamond armor/sword/tools as your end-game best gear, you can differentiate your armor types a lot. You can have leather armor that gives you a speed boost, chainmail that reduces knockback's effect, gold armor that gives you more than 10 hearts, wooden pickaxes with efficiency 10, and the list goes on.