I don't think that "simple" equals "only doing a few things". I don't think List::Util is much simpler than POSIX. They are both modules with a collection of subroutines. And while the POSIX module has the potential of doing a lot more than Class::MakeMaker - it's much simpler.
Adding functions to POSIX or List::Util doesn't make the modules more complicated - it doesn't become harder to use the new functions, neither does it make the existing functions harder to use. You just use the module, and list the subs you want to use. Class::MakeMaker suffers from the problem that there are so many ways of doing related things, that's why there's a lot of 'configuration' necessary, and that's what makes it complicated.