Maven is not a build script, it is a declarative build definition system. It is not supposed to be Turing complete, for things that need that customization, as

Maven is not a build script, it is a declarative build definition system. It is not supposed to be Turing complete, for things that need that customization, as the GP stated, you use extensions. For anyone who likes maven, checkout cargo in Rust. It got everything right, and made build extensions easier to integrate.