I've always taken issue with that term. Any guy who bathes, doesn't say mean things, tries to make himself more attractive, doesn't consider a woman unattractive because she isn't an 8+, and learns to strike up a conversation with the opposite sex will find someone sooner or later.
I don't know much about them, but people presented as incels generally seem unwilling to put much effort into any of that. If I had sat at home all day, played video games and really let myself go, does that make it involuntary or just lazy?