You are acting like the people we have had already have been great because of their "qualifications" All we get is crooked people seemingly not working in the people's best interests a lot of the times.
I disagree that we don't know the character of Hanks and Denzel. They have been in the public eye for a long time. Not only have they not done anything reprehensible, but I think most people can just tell they are good people. Acting is fake, but its also a peek into who they really are.
Plus, can you just imagine the speeches they would give? It would probably give you chills down your spine every time they spoke. The country as a whole would probably get a long better too.