That's why I've said "not just distribution guys".

include $(shell find . -mindepth 2 -name Makefile)

then have subsidiary makefiles say, in part, something like

ifeq ($(words $(MAKEFILE_LIST)),1)
all:
make -C .. # path to toplevel makefile from here
else
# everything else
endif

And now you have lots of independent fragments of makefiles drawing on a common library declared in the toplevel makefile, new ones are automatically picked up, the makefiles can themselves be automatically built using make rules and the changes picked up, and anyone typing make in subdirectories gets an automatic make from the toplevel instead. (With further trivial adjustments you can arrange to automatically build only the subdir's targets, and automatically compute the toplevel makefile, and have all of that boilerplate inserted with a single $(eval ...) so the people writing those subsidiary makefiles never need to know all this stuff.)

Not only is this not hard, it is stuff which it is quite easy to autogenerate if you so desire. It is also stuff which is designed into GNU Make (hence the auto-reloading feature of "include" if the included makefiles are rebuilt), so it is not in any way a "workaround".

(Non-GNU makes are often a lost cause in this area. Anyone who's not using GNU Make is just trying to be difficult by this point: GNU Make runs everywhere and is more capable than just about all the competition.)