Make is leaner and more agile than a custom CLI. It takes no time to get started, and there is no boilerplate. Removing or adding steps is trivial, running shell commands is trivial, and hooking into the dependency graph is trivial. Parallelism is built-in, as is dependency resolution. Tab-completion is standard on most Linux distros.

It's also better from an architectural separation perspective. Your custom CLI will have custom commands and flags, and probably will need to be called in some standardized way. Make is very good at calling your toolchain / build-system (whatever that might be) with the exact arguments that you want. And things like "make all" or "make clean" are muscle-memory for hundreds of thousands of developers.

Why mix your custom tooling with the task of standardizing an entry point?

I've had really great success over the years with the pattern of "some build system or another (cmake, bazel, autotools, etc) orchestrated by a top-level Makefile." It's simple, portable, and flexible. What's not to like, other than ugly syntax?