We've had a subscription for SI for 35 years, but it has turned into a shadow of its former self. It is now delivered every two weeks, instead of weekly. Our subscription runs out in a month and we won't renew. It will probably disappear in a year or two, if not sooner.
Let them know why you're not renewing.
As a kid, and throughout my twenties, I was a Sports Illustrated reader. Haven't been since the 1980s, though. Just not as much of a general sports fan as I was in my youth.