Actively welcoming new people isnt the same as actively recruiting people. There is a fixed number of incels in the world and that number can, technically speaking, only ever decrease. Unless they actively go out and convert sane people to their insanity.

You could argue that they can 'recruit' from a pool of vulnerable people who find them, but you can you can also argue that people in the incel group can leave as well.

This is where Scientology and incel's differ. You cant just log out of Scientology. They'll come after you. This makes incel's a evolutionary dead end.