The people who use AutoCad most likely use it for a living, and the time investment in learning the UI is probably worth it.

I feel the same way about Photoshop. People spend time learning its quirks because it's worth it.

However, realistically 90% of the features could be cut and it'd be for the good of the product.

The problem in the software industry (and this is not limited to Open Source) is that people like long feature lists.

This is especially important if you're a Photoshop or an AutoCad. You need new things for the new version.