Do not ride the bomb!

Even if SpaceX successfully lands the Starship 100 times, that still would not be good enough for human spaceflight, because there is no emergency system to save the astronauts if something goes wrong, either during launch or landing. The Space Shuttle flew 135 missions, and was still cancelled after just two accidents. Those accidents happened 20 years apart - not exactly frequent - but because there was no way to prevent them with the shuttle design, they fell back on the capsule configuration because it did help to address those problems.

Basically, the SpaceX Starship needs a capsule on top of it to provide minimal safety for the astronauts during launch or landing. That means the Starship is essentially a re-usable 2nd stage, and nothing more. That isn't bad though, considering SpaceX also has not yet successfuly re-used the 2nd stage. Also, if Starship is used to land on Mars or the Moon, having a capsule would not be useful there, only when it returns to Earth.