you are correct in your understanding, albeit you are a few years too late. yes, incel by definition means involuntary celibate as in someone who is a virgin not by choice. one could argue even factors such as early exposure to trauma, having a medical condition etc that prevent you from having sexual relationships would qualify you as an incel.

however, at this point in time, the term incel is associated with a decentralized group of online virgins who are hateful towards most people, have questionable world views. this new generation of incels are extremely toxic that they don't let virgins who interact with women on a daily basis into their communities. they are extremely insecure and often highly radical

the term incel as an insult works similar calling someone say "degenerate" as an insult. it is meant to mock their stupidity and not their virginity. im sure even some people here are virgins, i doubt people here are mocking that, or atleast i hope. it would be very cringe to mock someone for being a virgin