The Aaronic Priesthood isn't open to just anyone. It isn't just a spiritual calling. It's a physical, genetic one too, and only Aaron's sons are qualified. You absolutely must be a genetic descendant of Aaron to serve as a priest in the Tabernacle or Temple of YHVH. Neither priest of another order, Yeshua, Paul, pastor, nor rabbi are qualified to act as an Aaronic priest. (But remember that there are different orders or priesthood.)
Numbers 16:40