Reforge 3

Reforge 3 is the third modpack in the Reforge series (if you can't find Reforge 2, I deleted it), and leans more into the RPG aspect of Minecraft. You can create ultra-powerful weapons, or become an Archmage as you go through 4 dimensions on a journey for 12 eyes to unlock the portal to the End. You can go to the Nether, the Aether, the Eternal Starlight, and the Twilight Forest, take down their bosses, and forge new eyes from End Remastered.

Reforge 3 changes Minecraft in 3 main ways: The progression, the environment, and the difficulty. 

The progression is the main focus, instead of going to the Nether, then the End, you have to go through all the dimensions and get materials for crafting new eyes from End Remastered by killing bosses. In the Overworld, you have bosses like the Ancient Remnant, the Leviathan, and the Gatekeeper. From the Overworld, you can go to the Twilight Forest, the Eternal Starlight, or the Nether, where you beat bosses like the Ur-ghast, the Lunar Monstrosity, or the Netherite Forge. You can get Glowstone from the Nether and travel to the Aether as well, and fight bosses like the Valkyrie Queen or the Sun God.

The environment is completely different, with over 100 new biomes across the Overworld, the Nether, and the End. Biomes o' Plenty adds biomes like the Redwood Forest, and the Visceral Heap, some mods like Ars Nouveau, Nullscape, or Incendium also add biomes like the Quartz Flats, Weeping Valley, Archwood Forest, Void Barrens, Shadowlands, and the Crystal Peaks.

The modpack is also much more difficult than vanilla due to Improved Mobs. As you play in your world, the game will get more and more difficult every night. Once you go to another dimension, the difficulty will jump significantly, leaving the world even more hostile. Combine this with new enemies from Creeper Overhaul and Illager Invasion, and Nyf's Spiders making spiders way more dangerous, and you'll have a bad time. (Hehe, Undertale reference.)

Overall, the goal is to RPG-ify Minecraft while still keeping it aimless. The game is fine how it is now, but I think an RPG-like experience can be more fun for some people. If you're still reading this, thank you, and have a nice day!