The problem with handcrafted build system is only the author can effectively maintain it. When he moves on, someone has to spend the time ripping it out and replace with something more standard.

I've been on both end of this situation and would rather not do it again, so I'll use whatever is the de-facto standard, but you do you.

Any project effectively has a handcrafted build system, whether it's built on top of CMake, Bazel, Scons or built from scratch doesn't really affect that.

And if it's doing everything from scratch, it's more likely to be simple and self-contained, making it easier to maintain.