I don't think it's that simple. Sure, I could spend time figuring out the GNU Make source code. I could somehow shove a C preprocessor into it and make it automatically generate dependencies based on include directives. I could make it depend on clang. Will the make maintainers accept my patch if I send it their way, though? Somehow I doubt it. What if I changed the make language to make it easy and unambiguous to write paths with spaces and other problematic characters in them? Do you think the maintainers are going to accept a patch that will most definitely break existing makefiles that work perfectly fine just because I fixed a major limitation of the program? We're talking about a tool whose grammar requires that commands be prefixed with a tab just because the author experimented with that rule and then couldn't change it because about a dozen friends were already using it. Fixing make is simply not possible at this point. If you try, it will just become yet another incompatible tool, some kind of make derivative that will have to be maintained independently. At this point, why limit yourself to make? Might as well rethink the whole thing.

As far as GNU/Linux distributions go, make and autotools are the default. If you're using anything else, it's gonna be a build time dependency that people are going to have to install in order to build your program. So you look at the other tools and you find they don't quite do what you want either. They only do about 80% of what you want, and getting it to do the remaining 20% makes you really wish the tool was an actual programming language instead of a limited build script. Is it any wonder people roll their own?

Also, I believe people should work on what they personally like. There is no obligation to contribute to some project just because it's "standard". It's an interesting problem that's difficult to solve, so it's not weird to see lots of people offering their executable opinions on how things should be done. If programmers don't like what's available out there, they are welcome to try and come up with something better. Who knows what will happen? Maybe the new wheel will turn out to be better than the current one. Maybe it won't. It might introduce new ideas that will influence new designs. These ideas might even make their way into other systems.