Other countries don't directly pay for the pensions, but France is staring into a giant fiscal abyss because of their low retirement age (and other generous social benefits). Any attempt to change those results in the country being taken hostage by rioters, thus nothing changes.

At some point France will be in too deep shit and will look to the EU to cover for them. We will all pay for that. And it is deeply unfair because other countries their citizens have accepted later retirement and more frugal benefits to keep their countries fiscally healthy.

France could cover the fiscal hole in other ways, but taxing corporations and wealth at a higher rate also consistently ends up being blocked. And each year the hole gets deeper.