One ruling elder in the PCA has written a short essay addressing this issue. Here is a snippet...
What I believe has been lost in some of our churches, however, is the concept of the "Parity of Elders," by which it is understood that both orders of elders wield equal authority in the Church. This is contrary to many local church governments where the teaching elder or head pastor is assumed to have higher or special authority. In this model, the teaching elder/pastor is seen as a prophet of God, proclaiming the vision that the Lord has for a local church, and the ruling elders function as assistant prophets who carry out the vision pronounced by the head prophet. In larger church within the PCA, the teaching elder/pastor takes on the role of the church CEO and the ruling elders are middle mangers who provides an additional management layer to carry our the orders of the pastor CEO and to shield him from the daily demands of the congregation (my emphasis).
That last line is very important - "to shield him from the daily demands of the congregation." So if the shepherd doesn't do shepherding and if the elders don't do shepherding, who does it? In some churches it is relegated to the small group ministry or some other affinity group in the church. Others are more innovative and commission unordained men and women to do this work.
The author does more than raise questions but goes on to offer several modest proposals in the following article.
Ruling Elders in the PCA: Shepherds or Middle Managers?