I'm sorry it is frustrating. Perhaps too it is the age? At 21, some of your peers are still just getting a handle on basic one-on-one dating and communication skills. Poly-dating is a larger challenge. In my whole time as an teen/20's person, I only found ONE poly guy.
My partners were all mono. I was straight up with my wants, needs, limits -- but did not use the word poly. I did not know it then!
But I was clear about not wanting to be exclusive at this time, and they could see, date, be with whoever. All I needed was the safe sex heads up so if one of theirs was looking to go loverly I could make a health decision for myself and decide if I wanted to overlap or not. I felt that was fair.
Basically I was a baby poly chick living
it, but not knowing the WORD for it.
Some were not down with it at all. Some were willing to try. Some bailed after realizing the realities. Two hung in there.
I do not know if that helps you any.