If you don't want to mess with text files, you can use a "Fullbright" texture pack. These are popular because they don't require Fabric or Forge to run.
If you plan on submitting runs to official leaderboards, be aware that many categories forbid setting your gamma higher than 5.0. Minecraft FullBright with NO MODS Tutorial Fullbright 1.17
To get in Minecraft 1.17 , you essentially have three paths: editing your game files (no mods required), using a resource pack, or installing a dedicated mod. 1. The "No-Mod" Method (Gamma Editing) If you don't want to mess with text
The Fullbright mod on Modrinth is a lightweight choice for 1.17. using a resource pack