I would not say that nuances were lost. At most, word usage and the way nuances are expressed have changed. People from the 1910s just happen to make use of many words that have fallen out of use for the people living in 2021.

Someone from 1910 would have a hard time understanding all the neologisms that were introduced after two world wars and decolonization until today.

For us from 2021, someone from 1912 uses words that are commonly found in written works from the same period (and after). This is why we feel it sounds like 'art'. Written words live way longer than spoken words.

Even today, common spoken French is very different from common written French.

But what has that to do with making an art of speech? Nothing to indicate literacy has made speech "unartful".

It has gained new nuances in the process. I wouldn't call it a simplification, given that foreign speakers often struggle with some of the finer points of slang.