I agree with what's already been said, but want to add that you might try "advertising" at your LBS for other riders more like you. They might want to do the club rides, too, and then you could begin to form your own little "back of the pack" sub-club. In the club I ride with, the riders at the back are Sweet Sixteens--we stay right around 16 mph on average. You could try organizing your own little Sweet Sixteen group (or whatever the equivalent is in kph). Or plan your rides to nice lunch spots, ice cream shops, whatever.

You can make it fun again, and get the love back. Just give up the speed and the hard work that made your rides more like work, less like fun.