Bishop Bruskewitz follows the GIRM, which means there are lay lectors, communion in the hand, communion under both kinds, Extraodinary Ministers, and references from non-Scriptural sources quoted in homilies in churches in his diocese.
So, it must be something other than liturgical practice that is responsible for increased vocations.
Correct.
which means there are lay lectors,
It doesn't mean that at all. The GIRM permits but does not require lay lectors.
communion in the hand, communion under both kinds, Extraodinary Ministers,
Again these are practices permitted but not required by the GIRM.
One can eliminate all of them and still be in full compliance with the GIRM - and generally in better compliance to boot.
and references from non-Scriptural sources quoted in homilies in churches in his diocese.
This is a straw man you invented. The document concerns readings given at Mass from non-Scriptural sources. There is no proposed ban on quotations from non-Scriptural sources in the homily.
So, it must be something other than liturgical practice that is responsible for increased vocations.
I think that if you randomly attended a Mass in one of Lincoln's parishes and randomly attended a Mass in one of Chicago's parishes, one would find a highly marked difference in liturgical practice.
I lived in Chicago for six years and never attended a Mass said in conformity to the GIRM except twice at Opus Dei Masses.