Today's Ron Leary is not better than Joe Looney, at least not healthwise and also due to age. Plus, Looney can play both Guard and Center very well. That puts Looney above Leary.
Then we've got the two young stud Guards in Connor Williams and Connor McGovern. Plus, add in veteran Xavier Su'a-Filo. Then add in their backups in Cody Wichmann and Adam Redmond. All of them are young and definitely much younger and healthier than Ron Leary.
I don't see how Coach McCarthy would want to bring back an old, over the hill, constant knee injured Guard back to the Cowboys over any of the much younger and healthier Guards we currently have?