In the smaller city, I took buses or walked, but I noticed taking a bus still makes a difference, even though one might have to stand up a little. Just the idea of being surrounded by people, each with their own untold stories and problems, made me feel part of something bigger. I agree with the OP; commuting actually helped me feel like I belong to a community, even though I'm introverted and would never talk to any of the people that I would see.
Now with the pandemic on top of it, depression has kicked in. I sometimes play youtube videos with city/car/library... ambient sounds, just to get that feeling again. It does help a bit, but I can't wait for things to get back to "normal", whatever that means from now on.