The full site has nothing to do with whether the mobile one has failed in UI. The problem is that many full sites have not taken the time to properly develop a mobile one. You CANNOT expect a mobile site to have all the same functionality of a desktop site because there are far more things to interact to and with on the desktop site.
Therefore, a mobile site MUST have more limited functionality in almost all cases because reading is limited, you have limited typing ability, no mouse, and you are most likely moving about so a bouncing screen.
If you have to zoom in to make a mobile site work, then the site was either not designed properly or you shouldn't be doing that on a mobile device in the first place.
Native apps can be faster but aren't always necessary. As time goes on, more of the native stuff will be available through APIs.