The courts struck down the 2005-2010 structure in 2010, and the 2010-2014 structure in 2014. 2014-2015 was unregulated, but all actors knew that the FCC was going to come out with some new neutrality regulation, so no big player was going to put effort into exploiting the unregulated state and build an unsustainable business model around it.
It is impossible to return to any of the three states of neutrality enforcement that existed between 2005 and 2015. And Ajit Pai knows that, so if he's calling for that it is intensely dishonest.