Yup, "It's a Wonderful Life" is a great film and is B&W, no sex, no violence, etc
I am not sure it is B&W films, but the skill at the time was probably greater in the story telling and the cinamatography. However contrast to the "Lord of the Rings" trilogy and the scope of the stories and the CGI make Clarence in IaWL seem a poor rendition of the fantasy, both Golom and Clarence are imaginary creatures, they are treated very differently.
BUt there were many rubbish films made in the past, only the best (however defined) survive.
I have a friend, an architect, who was asked why modern architects so rarely produce great buildings. His view was that there are probably more great buildings produced today, the reason we see old buildings as bing 'better' than new is because all the crap ones have fallen down or have been knocked down. Same for films?
R