I don‘t mean to discuss which system is too complicated and which is not just to point out a lot of real world build systems are on that level.
Gradle wrapper is just a name for a script (automatically created by Gradle btw) which allows one not to have any kind of Gradle-related tooling installed on the machine (basically, to run build tasks you execute `./gradlew someTask`, and it takes care about downloading and running the appropriate Gradle version) - which I think is a clear benefit over the fact that you need to have `npm` installed system-wide or via a tool like NVM in order to build JS projects.
Gradle has its own warts, and a lot of them, but at least there is only one major build system in this area, and it is simply impossible for a library published to a Maven repo to be dependent on the build system it is built with.