Are you saying that some people’s lived experience doesn’t support their own existence mattering? If so, (1) talking to loved ones or a therapist might change that perspective, and (2) if that doesn’t work or isn’t an option, you can find a purpose for yourself. If you find something you believe in, or something that you’re glad exists, that you can contribute to even if only in a small way, you’ll probably find yourself seeing that your existence can and does matter after all. Even just answering people’s questions on Lemmy makes a little bit of a difference. People commenting here have helped me; even if I stopped believing all humans inherently matter, I’d say all the anonymous people who have helped me and others with our questions matter.