As a native French speaker, I have to say that the biggest drawback for me was the very anachronistic nature of the dialogue. There was no effort to mimic French as it might have been spoken at the end of the 19th century. Instead, we get modern swear words, modern turns of phrase, etc. Sure, some of them already existed back then. But the story still takes place more than a century ago and you'd expect some effort to reflect this in the dialogue. This very modern spoken French cheapens the movie and turns it into some kind of extended-play sitcom. I didn't find Canet all that convincing as Zola either, partly due to the script and partly due to the acting and physical transformation (or lack thereof).
Review of Cézanne et moi
