People don't have independent mobility now. The majority of cars are not designed for off road and therefore can only go where there are streets. If public transportation provides the same access, then there is no loss of mobility.
Well yes, but in 99.9% of cases, there are roads to where you want to go. Public transport is not independent. Live in a rural area? Fsck you, no bus/train for you. Have a large dog? Nope, no transport for your dog. Want to travel at 3 in the morning? Nope. Need to carry stuff with you, more than you can carry? Nope. Want to go to a protest? Nope, no buses/trains driving there today.
That's why the post that started all this expressed a desire to live in a future where people could replace their cars with public transportation as opposed to advocating that we get rid of all cars now. Currently public transportation isn't viable for many people, but it would be nice if in the future it was.
That being said, I think that you are overstating some of the limitations of public transportation. The NYC subway runs 24 hours, allows dogs, I have taken it while transporting 200 lbs of steel before, and it did not stop running during the George Floyd protests (including after curfew).
