If you are selling your site to design hipsters, I have no problem with the bloat: they have plenty…

If you are selling your site to design hipsters, I have no problem with the bloat: they have plenty of money and plenty of bandwidth. If your site is intended for anyone outside that community, usability is paramount. Nobody leaves a useful site on the basis of looks, but they absolutely will leave a useful site on the basis of bloat; if looks are the determining factor for your site’s traffic, then it doesn’t serve a useful purpose.

A piece of JavaScript that loads a link to a properly-made site once it has detected that the bloated version has failed is yet another piece of bloat that can be expected to fail. Why not default to the clean site and provide a link to the fancy one?

It’s perfectly possible to build a clean, good-looking site without relying on large amounts of complicated CSS and JavaScript. Certain behaviors are not possible without these mechanisms, but these are behaviors that should be avoided when possible because they cannot reasonably be expected to work for most users.