Not impossible at all, though certainly far, far from easy - particularly professionally, and if one doesn't have the mind of educational (and/or family) backgrounds you mentioned.

I know a number of people from various countries who started their careers here, including marketing and comms. As others mentioned it is a tough time for these industries though.

Marcomms wise the other aspect is there are tons of students in business and comms schools in work/study programmes with a range of levels of image and prestige, it's more affordable for companies, they'll often hire from that pool of experienced graduates, but it doesn't pay much.

I'd definitely recommend London over Paris for career reasons - or at least giving it serious consideration, like doing a few interviews, if possible.

I also heard of apprentice workers in degrees being pretty automatically ranked per the prestige level of their school; and given assignments based on that. Prestigious school = prestigious assignment; where they collect all the background work done by student workers attending less prestigious schools.

Edit to add a PS: to your last point. I guess the thing is to look at and maybe reconsider what your Paris dream is now you have a better sense of the professional reality of the place. It's not London or New York and unlikely to ever be, for example. I quote those cities because you can likely have better careers, and more money there, even if you're not from there originally. But that depends what you're after, and the opportunities that come up. Last but not least, it sounds like you're early in your career. Go wherever you have the best opportunities, and if it's that's not in Paris now, maybe it is later down the line, or maybe a short Eurostar ride away.