This particular thread is one of the more useful discussions on the aesthetic trends in 40K that I've seen in a while, going beyond level of detail, phwoar factor and producer ranking. It's at BoLS believe it or not, on a more or less ephemeral post.
One of the arguments corresponds to that idea that D&D is now its own set of reference points, which came up again with the nods to past fiction in fifth edition. A couple more: