inb4 turn down the difficulty slider
No offense but seriously why not just do that? OOO's main purpose is NOT to make the gameplay harder, it's to make the gameplay.. worthwhile. It adds things like, rewarding the player for leveling up, hand-putting items in dungeons and making the contents of chests a little more variable and surprising, so there's a point to exploring, varying the difficulty and number of enemies so that each encounter feels different instead of just a slow grind, etc. You'll still get all that if you tone down the difficulty slider.