Maven is actually very important since it is a "generic" project format that all IDEs understand, it handles dependency management/downloading, etc. Ant and Gradle are nowhere near as useful since they are not a format an IDE can understand natively. They are a build script, not a project file, so you need to keep another project file in sync for each client you're using.

You don't even necessarily need to be building a Java target for Maven to be useful. It's also a common way to build continuous-integration build scripts for things like Docker packages, database artifacts, etc.