A good public transport system is not difficult for families and even easier. Berlin has a pretty good public transport. We had a car when we first moved here (we're a family) but we never had the need to use it other than 1-2 occasions in a year because public transport + biking is easier, faster and more comfortable.

At the end we got rid of our car and not planning to buy another one. For those occasions that happens 1-2 times a year, we just use a car sharing app. It's also a lot cheaper than maintaining a car.

Sadly, Paris is not that. It's a great public transport system without families, but not for anyone with young children or with mobility problems. I can make do, but only if I have my 18 mos. old in the stroller OR my 3 year old walking, but not both. (It's a bit easier for my wife, because people will stop and help her up and down the stairs with the stroller.)

Buses do tend to be a bit easier if you're travelling outside of peak hours. Otherwise, you might have to let a bus or two pass you before one comes with enough space for the stroller.

Things are supposed to be a lot better with the Grand Paris Express, although that won't help much intramuros.

To be honest we're moving out of France. I don't see much future in this country if you have a family unless you go to somewhere like Auvergne where there's less jobs, mostly farming and these guys are getting decimated and cities run down. Owning a dog here starts to be higher virtue than having a child. French are moreover delusional about the role their country plays in the international scene and lot of other things. I give it 10-20 years max.