For the technical player, darkness is inefficient. It forces the player to stop, place a torch, break it, and move on. It reduces the "flow state" of mining or exploring. The Fullbright texture pack exists to dismantle this friction.
If you see this error, you used pack_format: 4 or higher . Go back and ensure your pack.mcmeta has "pack_format": 3 . That is the correct format for 1.12.2. fullbright texture pack 1122 link
Minecraft Java Edition 1.12.2 (released September 18, 2017) is a long-term modding hub. Reasons include: For the technical player, darkness is inefficient