Is it a good idea to do a (cs) phd in France with a fixed topic? For what I know, one finishes PhD with only 3 years in France which is rather efficient, but one may suffer if one's research interest gets changed in the mean time, because the thesis topic is locked by the funding and by the advisor right from the beginning of the PhD, which could be disturbing in a fast changing field like cs. Besides, PhD programs in France don't seem to get global recognition as the ones in the US or even some in the EU, with one or two exceptions. Even within France, PhD is condemned to belong to the academia and is rather ignored in the industry (if there's any).
Could anyone familiar with the French system correct me on this? Is it possible/typical to research on a different topic from the one that I'm getting paid for, to change the PhD topic, or even to quit the PhD in France?
Thanks.
Most of your questions are field-specific, so as a physics PhD student I might be a bit off the reality of CS. Still, here are a few hints:

the thesis topic is locked by the funding and by the advisor right from the beginning of the PhD

This is only true in principle. If you don't have any obligation of obtaining a particular result, things are not that black and white: a PhD is about investigating some ideas, which for instance might turn out unfruitful and need some more or less drastic changes.
Depending on the advisor and funding entity you may also simply switch your research topic (if this is a relevant move -scientifically and timewise-, of course!).

PhD programs in France don't seem to get global recognition as the ones in the US or even some in the EU, with one or two exceptions

Recognition first comes from (i) the quality of the work, and (ii) how you communicate about it. That's where working in a team with good connections with the community can help getting your work known in your field. Attending conferences is also a must!

PhD is condemned to belong to the academia and is rather ignored in the industry

If the skills acquired during your thesis can be exported to industry, finding a position in industry afterwards is far from impossible. As an illustration I've seen quite a few students in theoretical physics move to data science or machine learning straight after graduating. Doctoral schools are aware of this, and some (if not all) organise events to put students and people from industry into contact.

Is it possible/typical [...] to quit the PhD in France?

Afaik, there is no official data on the dropout rate of doctoral students in France. But quitting is absolutely possible a not to be ashamed of. A PhD is a three years contract, which you have the right to resign by formally notifying your employer. (Note that you can't just notify them and leave, there is a legal period to be respected.) On such kind of matter, checking on this official page can be helpful.