I expect downvotes for saying this, but the priest has very little discretion in this matter. If Archbishop Cupich says Catholics have to wear masks to Mass in the Archdiocese of Chicago, then Catholics have to wear masks to Mass in the Archdiocese of Chicago, and the diocesan priests have to enforce it.

Diocesan priests take a vow to be obedient and loyal to their bishop, and they have to uphold it, even if they don't like it.