Having played Skyrim since release ... I can almost totally agree with the OP. Seriously just take a look at the bug fixes in the UNOFFICIAL PATCHES. Seriously it's like the devs never even tried.
O.o the bug fixes in most of the unofficial patches are mod work fixing. making them compatible with in game stuff. Think people are missing what modding truly is. it's just editing what is already in the games code. Most mods are not brand new core coding.
They take code from the source and just edit it, making it do something else...that coding doesn't just come out of thin air O.o The company making the game makes the core. What it can handle and do mod wise is based off that.