Aesthetic isn't easy to program.
Of course not. It would be foolish to leave it entirely to
an algorithm to design a game. But who said an algorithm
would be in charge of high-level design qualities such as
aesthetic? The procedural methods I'm referring to are the
kind that would deal with the minutiae, but allow the designer
to create at an ultra-high-level.
Take for instance, modelling a brick wall. Instead of a
modeller pushing vertices and adjusting UVs of individual
bricks, he could say "build me a wall, make the bricks out
of red clay, make it more worn here, put a stain there, poke
this brick out a little.", etc
That is just one application of procedural content generation
and there are kinds that could be much more automatic, of course.