This is the scene that sold Taxi Driver to me years and years ago. It's not one of the "iconic" scenes in the films that everyone talks about. But it showed Travis wanted to fit in, wanted to be a good person, he just needed help and didn't know how.
I can only speak for myself, but I find that that those who have grew up around those on the spectrum, this movie just rings a bit differently. Same thing for Wes Chatham/Amos Burton from The Expanse. That character just resonates deeper with those who have been around more functional autism. ( Not implying you of course)
A film I thought carried some of the core themes of Taxi Driver was, bizarrely enough, The Homesman. There's a scene where Hilary Swank is talking to an old shopkeeper in town, and he points out that "no one ever talks about crazy", that people just stare in silence, because it makes them uncomfortable.
My take on Taxi Driver, and the dubious aspect of mental health in films, is that we are all biologically hardwired to survive and reproduce. And those who show signs of mental health struggles, that's an instinctive red flag. That many don't want them in their bloodline, not in their family, not in their communities. It's why Travis was outcast. And it seeps a bit into why Hilary Swank and Tommy Lee Jones were also functionally isolated in The Homesman.
Sometimes I think that's the worst kind of human tragedy. Someone who doesn't want to be broken anymore, but they don't know how to ask for help and they don't even know what questions to ask. And they don't encompass the kind of social status or social "value" that will incentivize someone else, anyone else, to bother to care. Just some thoughts.