Ticket sales actually aren't as bad as you make it sound. For starters, on Ticketmaster, under "type", uncheck the resell tickets. Once you add up all of the available seats, it totals 3,804. For some reason, Ticketmaster has stopped showing the number of remaining available GA tickets; but I'm just going to guesstimate it as roughly 2,000, which would bring the total number of available tickets to 5,804. According to Wikipedia, the stadium has a total of 55,000 seats. Some of the seats, roughly parallel to the stage, are blocked off for sight purposes; but, the volume of available GA tickets likely more than makes up for those lost seats, probably bumping the capacity for this show to roughly 57,000.
With all of that said, based on my estimate of 5,804 available tickets (again, 3,804 remaining seats + what I expect is as many as 2,000 remaining GA tickets), that means that, at present, the Louisville concert is 90% soldout.
I speak for none but myself, but I think that being at 90% soldout thus far is pretty damn good. As today is March 20 and the concert isn't until June 16, I expect that most, if not all, of the remaining tickets will ultimately be sold.