During the novel in chapter 31 Jane mentions Marseilles, she says, "Whether is it better, I ask, to be a slave in a fool's paradise at Marseilles--fevered with delusive bliss one hour--suffocating with the bitterest tears of remorse and shame the next--or to be a village-schoolmistress, free and honest, in a breezy mountain nook in the healthy heart of England?" She refers to Marseilles as a "fools paradise" alluding it to be seductive, luxiours, etc. She finds herself day dreaming about a life with Rochester there, although she would be his mistress, which would be very degrading to her. The mention of Marseilles in the text is more of a contextual evidence of passion and lust without logic.
Now during the 19th century Marseilles had a reputation for being blue collar, compared to its neighboring cities Nice and Côte d'Azur which houses yachts and villas. This differs greatly from Rochester and even Janes lifestyle- therefore choosing Marseilles would be like hiding and only moving there to be together where they assume no one would know them since they are in such a different social class. Marseilles also developed a reputation for violence and criminality during this time era. From the images I found it doesn't seem like Jane would fit in with these types of people either.
The location illustrations show people crowded by a rock seeming to be having a little party. This is almost the complete opposite from Jane Eyre as she is quiet and reserved. Another photo I added shows the busy streets of Marseilles which I think is completely different then what Jane is used to living at Thornfield with Rochester, no quite rolling hills in a secluded estate but busy bustling streets with lower class people. Therefore, I don't think she would fit in well with the people in Marseilles and I think it was a good idea that she decided to end up going.
References:
https://daily.jstor.org/marseille-independent-industrial-and-mediterranean/
https://www.literaturepage.com/read.php?titleid=janeeyre&abspage=432&bookmark=1#google_vignette