Yeah, so how do you fold a Yoyo with a newborn in the arms? You can't really, and some stations have a lot of stairs. Regarding drug addicts, I saw many, it really depends on where you live. My son was born in Paris, and we left as soon as we could because it felt really stupid to endure all of this. Buying a car felt like I discovered a time travel machine.
You can leave the newborn in the stroller and lower the whole thing yourself or with someone’s help. You can hold the newborn and ask someone to fold the stroller. You can take the bus or the tramway if you really want to avoid the subway.
Tramway doesn't go into Paris, and asking someone to fold a stroller multiple times a day- no, just no.