> Local parks and generally streets are so dirty that you have to wash your children from head to toe as soon as they have set foot outside.
Maybe if it is a newborn, and if you don't bring the stroller nor any clothes, on rainy days it can be that bad. Don't get me wrong, Paris is not a clean city, there are empty nitrogen tanks, puffs and cigarettes lying on the ground pretty much in every arrondissement, but syringes, even on the colline du crack I can hardly remember having seen even one (but it is very dirty there! with packaging, paper, cardboard, bottles).
I still think there should be a higher priority on sanitation but I also think you are exaggerating a bit.
We were gifted a big heavy modern stroller and almost never used it, when the kids were babies we wore them and now they can walk a little we just do that and take breaks. If it's going to be an all-day thing (like a theme park) we'll bring a lightweight umbrella style stroller and those are trivial to fold up and carry.
The accessibility argument makes sense for folks with disabilities but not so with children.
I loved carrying my kids as babies, and rode them everywhere on my bike, but there will always be people for whom bikes, walking or cars aren't an option, which is why accessible public transport is always important.
A week with a double stroller in Paris will make you appreciate ADA wheelchair ramps, kerb cuts, and elevators.
> Local parks and generally streets are so dirty that you have to wash your children from head to toe as soon as they have set foot outside.
That's an insane hyperbole.
> And I'm not even talking about used seringes and broken glass in certain parts of the city.
Not my experience, at all.