What can a deacon do?   They can distribute consecrated  hosts.   After a priest has consecrated them, that is.

But deacons can't marry people, or say mass, or give extreme unction.  They can't hear confession, can't ordain others into holy orders.

Deacons can preach.   But the church doesn't need more preachers.   It needs people who can administer the sacraments.    I.e, priests.

I mention all this for those who believe more deacons would somehow help solve the crisis of the dearth of priest vocations.