For a single developer I think it works OK to review pbxproj changes like other source.

You really should understand and recognize what each change is.

It’s when you have the additional dimension of multiple developers changing the project that it really becomes unwieldy and you are pushed into treating it as binary.

If you are already familiar with Bazel or don't mind spending a week to learn, sure. I manage all my personal projects in Bazel as well.

Otherwise, many people have positive experience with XcodeGen and that is more close to Xcode project format than Bazel. Besides, you can continue to use Carthage / CocoaPods with that.