Wastify
With this mod you can alter worldgen. It allows you to replace biomes or blocks. Replacing blocks is expensive so be careful with that! In the configuration you can define a mapping between biomes and a mapping between blocks. The main purpose of this mod was to allow you to make a world look like a wasteland but it can also be used to get rid of biomes that you don't want. Or get rid of blocks you don't want in the world (like water).
Usage
1.16.5
To use this mod you first have to edit its configuration. By default this mod doesn't do anything. This mod is intended to be used with the default world type.
1.18.2 and 1.19.2
In this version there is a preconfigured overworld.json which will convert your landscape to desert. To override this you need to make a datapack with your custom overworld.json. More documentation will follow later
Screenshot
Here is an example of a world converted to a wasteland by this mod:

Modpacks
This mod is free to be used in any modpack. Let me know if you have issues. And warning! The block replacement feature really makes worldgen a lot slower. Use at your own risk!
How to Install Wastify (Mod)
Wastify by McJty is verified for Forge across Minecraft versions 1.16.5, 1.18.2, 1.19.2, 1.19.3, 1.20.1 (latest release: 1.20-3.0.0, file size: 15 KB). Follow the steps below to install it safely from ModCraft.tv:
- Click the Download button above and select your Minecraft version (1.16.5, 1.18.2, 1.19.2, 1.19.3, 1.20.1) and platform (Forge).
- Make sure you have the compatible loader or environment installed for Forge.
- Move the downloaded Wastify file into your Minecraft
.minecraft/modsfolder and launch the game.