"It is not realistic to expect to find ‘net nets’ like Ben Graham did in the first half of the 20th century."

This is definitely not true. There are lots of net nets out there, even in 2017, and a lot that fit what Graham was looking for in net nets in his day. Net Net Hunter (www.netnethunter.com) has a lot in the Raw Screen at the moment and some good quality picks in the Shortlist.