I don't think it's a matter of Reinsdorf not caring anymore. I figure he's about at that age where he's decided to turn over some of the decision making to others in the organization. And that means he becomes less visible on a day-to-day basis.
When he bought the team in 1981 with Einhorn, the Sox had a big uphill battle to fight. The franchise was down, the park was in terrible condition, and the fan base was bottoming out. Naturally, they pulled out all the stops and made the Sox relevant again on the Chicago sports scene by signing Fisk and win the Western Division by 20 games just 2 years later.
Do the Sox seem to be trending downward as far as popularity is concerned? Let's just say Sox fans have a "show me" attitude, unlike fans on the other side of town. When the Sox aren't winning, the fans stay away. It's been that way for many years. And this year's team has shown so far that's it's nothing more than a .500 club that is unlikely to threaten for the division title. There are just too many holes and weaknesses that become evident over the course of a 162-game season.