Shatner's job on Rescue 911
was to host. That's all. Introduce and link the segments. Did he do that? Yes. Then he's done all he was asked to do - and all that anyone has any right to expect from him.
Just because one hosts a show does not mean they should be expected to know everything about its subject matter. No one seriously thinks Robert Patrick is a cop just because he narrates Disorderly Conduct
, or that Liam Neeson is a mountain climber because he narrated the IMAX Everest film, or that Morgan Freeman is a NASA scientist because of his work on Cosmic Voyage
, etc. etc.