Okay, I spent all of my late teenage years to early adulthood in France so I feel I can chime in: French people, like most Westerners I've met, don't know what they should do with their lives and the burden of responsibility of having children is simply not that appealing compared to having fun, either partying and doing coke or collecting figurines and dakimakuras. Even romance and love is fucked because marriage is seen as outdated and so serious so life long monogamy, for many, is just meh or scary. People don't date for any objective, they just get together cause they're lonely or sexually starved. And if they do understand what they should be doing, they'll be old and weary, and either the psychological scars will stop them from fully commiting to something or biology will have done its thing and now you're 42 trying to have your first kid, of course it's gonna be difficult.
Now, whilst I have my value judgement on it, I'm not making any right now, I'm just describing what I'm seeing. Hedonism, consumerism, and an ideological vacuum, means that people won't be making big commitments like having children. Of course the Muslims will, that makes sense, no surprise over there.
PS: and no, it's not a financial thing. The immigrants with no support or family money that goes back several generations, working shitty min wage jobs, have and want to have children. It's an ideological difference.
PS2: oh yeah and the current wave of redpill and casual misogyny on one side and "sexual liberation" and casual pornography on the other isn't helping either. It just makes both sexes less interested and more cautious, even when there's always good people in the bunch. That's gonna have to be addressed as well.