Hey, Please maintainer here! One of the big differences to the other Blaze like build systems is Please actually doesn't treat any of the built in languages any differently to other languages. They are implemented entirely in the build language which is totally open to you as a consumer of Please.

Another big difference is Please is written in Go so there's no dependency on VMs or runtimes.

Bazel is moving in that direction too—the C/C++ rules are built-in, but they’re slowly being extracted into Starlark.