The sample looks quite different from the README.md example, either way, doesn't appear to work?
Method com/github/hexomod/replace/token/PreprocessorExtension_Decorated.getExtensions()Lorg/gradle/api/plugins/ExtensionContainer; is abstract
 
plugins {
    `java-gradle-plugin`
    kotlin("jvm") version "1.6.10"
    id("com.github.hexomod.replace.token.preprocessor") version "0.3"
    id("com.github.hexomod.macro.preprocessor") version "0.8"
}