Dungeons (including daily duty roulettes), FATEs, challenge logs, levequests (those these aren't available in Stormblood areas, and are also best reserved for crafters/gatherers). There are more ways than that to level. POTD is just considered the easiest/most efficient way (well, the latter is for DPS only really) to level. Get in an FC that uses the increased XP buff to make it shorter work. If you're forcing yourself into POTD only and getting burned out, I'll be brutally honest and say that's on you. The game however does NOT force you.