Best practice is to keep it simple. For example, if the Makefile is written in such a way that lazy set or immediate set doesn't matter, then it is not complex

Best practice is to keep it simple. For example, if the Makefile is written in such a way that lazy set or immediate set doesn't matter, then it is not complex at all. But these facilities are there for achieve logic. Complex logics are complex, especially when they are entangled. For example, we often use build tools to generate Makefile. Some of the logic is implemented in the build tool; some of the logic is implemented using Makefile -- of course the result is complex. There is no rule of thumb on how to organize complex logic, that is what programmers are paid (so much) to do. Respect your job and treat complex logic carefully, then you won't make too much a mess -- at least do not complain about it after making one.