Great eggs but not joining

I work with mainly progressive and lefties in the social ngo sector. We have had all of the Gen Z people in the org except 2 say they won’t join the union. Most are new at work, and would not have known much about unions. A lot of their jobs were in hospo while at uni. They said they will “form their own union”, that “won’t prohibit people based on cost” and want their demands with our EBA. We have had no issue about the eba with them. I have been talking about special leave they have proposed which is great but they want full participation, even call themselves “union” but just don’t want to join our union. Which means our resources, officials and expertise, without combining their resources with us. I am so frustrated about it. They should be folks who are signing up and not need so much of my time as a delegate. I love these guys, they are really caring, empathetic people and I am trying to be patient. I also know they would bring the workplace together as they are social leaders in the org.

I think being not young, I am seen as a bit of an older woman and my thoughts are probably not speaking to their language?

Can anyone suggest ways to like get young progressive folks to join us? We have our EBA negotiations next year.