As for people with disabilities, die young, and/or have other factors that impede their ability to marry, a rabbi told me (and I also read it somewhere) that sometimes souls come into this world to complete a mission without their beshert.
Someone’s soul may have one last mitzvah to accomplish.
We never know what we were destined to do here, at least certainly. Thus, one cannot just say, “Oh I don’t need to get married because I have a feeling that I did it in my last lifetime.”
At the same time, if someone has a different-ability, that does not include getting married, then that person is not obligated to perform that mitzvah.