Reformed preachers study the writings of our church fathers for many reasons.
One reason is that new heresies are just the old ones, brought again by Satan to harm the church.
This is why the great Puritan, William Perkins, admonished preachers to “get help from orthodox Christian writers, not only from modern times but also from the ancient church.”
Reading our church fathers reminds us that no error is new under the sun, and it readies us to handle these pernicious problems.
“We do not need to look for any novel way of rejecting and refuting heresies;” Perkins wrote, “the ancient ones found in the Councils and the Fathers are well-tested and still reliable.”
See William Perkins, The Art of Prophesying, 24 for these quotes and for a list of ancient heresies matched with the ones Perkins was facing in the late 16th and early 17th centuries.