Its literally underground. Anyone that has a wheelchair, old people, blind people etc are not gonna enjoy using it. Elevators are often out of order and even if not its a hurdle.
Ramps, escalators, tiles, and seating. There is nothing inherently not accessible about subways, we just choose not to make them accessible. When I was in Japan, there didn't seem to be any issue preventing wheelchair users, old people, or blind people from using the train system. Escalators can be used by people in wheel chairs and old people (and presumably blind people too, but I'm not sure.) There were tactile tiles in the floor to guide the blind, and there was plenty of seating specifically dedicated to old people, disabled people, and pregnant people. There were also wheelchair accessible cars on every train. As far as I could tell, it seemed just as accessible and easy to use for them as anyone else. (Also elevators were only usually kept open for the people who needed them)
But... They are literally not. My family never had the ability to move to any house they want because everything needs to be accessible on the ground floor.