The defining feature of Bazel is sandboxing build steps so that you can't accidentally miss edges in the dependency graph. This has enormous benefits:

1. Incremental/cached builds are reliable.

2. You can reliably avoid rebuilding/testing artifacts that cannot possibly be affected by a PR.

Neither of those are possible in build systems that don't do this sandboxing. If you're doing a big project you really need these, hence why Google came up with this technique.

I'm not sure there's much value in a new build system that doesn't even get that right. We already have dozens.