Whaddaya mean he's not exciting?
Here he is, undercover as Ed Markey, scaring children during the Iran nuclear deal hearings.
Umm, frightening children like that is not a positive.
https://www.youtube.com/watch?v=Bkyyp6eBqUQIt goes against Hillary's best argument against Trump, which is that Trump lacks the seriousness and self-control to be commander in chief.
Anyway, the reason why nobody talks about Kaine is because he seems to be basically a fake Hispanic. If Kaine is picked, it will look like Hillary wanted to pick a Hispanic, but couldn't find any that she liked, so she decided to pick a substitute fake Hispanic who speaks Spanish who checks the ordinary white male boxes and is from an important swing state, but can also sorta-kinda-but-not-really appeal to Hispanics. If you are going to do that, might as well pick a real Hispanic. Hence the fascination with Castro, Beccera, Perez, etc...