Did you read the CC0 link I shared? It has something to say about this. Quoting the relevant part here:
"More challenging yet, many legal systems effectively prohibit any attempt by these owners to surrender rights automatically conferred by law, particularly moral rights, even when the author wishing to do so is well informed and resolute about doing so and contributing their work to the public domain."
I am not saying it is impossible to give up your proprietary rights in France. I don't even know what the laws of France are. But it definitely does not seem like a simple process. For example, almost every license has a separate section dedicated to disclaimer emphasized in either all caps or italics. Those disclaimers are necessary for various reasons or you might be held accountable if your software does not work correctly or, worse, if it causes damage to users. So even if you were to share your work in public domain, what do you do about the disclaimer?
Are you willing to take the risk of omitting a well-written disclaimer drafted by laywers and open yourself to the possibility of being sued by someone because your software did not work the way it was supposed to? If you are going to add a disclaimer there anyway, then you no longer have the benefit of avoiding the overhead you wanted to avoid. In that case, you might as well go with CC0 or a minimal license like ISC, MIT, etc.
The various open source and creative common licenses were made exactly to help creative people like us who are not trained in law but who understand our domain of creativity well. These licenses allow us to be creative and share our creativity with the world without having to worry about whether public domain is applicable in a certain country or not, what the legal framework for it looks like, whether we need to add an additional disclaimer or not, what the precise wording of the disclaimer should be, whether the disclaimer would be valid in other countries or not, and so on.
By the way, I believe I understand quite well where you are coming from. About 15 years ago, when I began releasing some of my hobby projects as open source software, I too wondered if I couldn't just publish everything into public domain. After a lot of discussion on IRC channels, learning from the experts, and reading about open source licenses, I realized it is just simpler to take a well established open source license and use that for my projects.
Disclaimer: I am not a lawyer. This is not legal advice.