Digg was a different culture. It was a lower-effort culture but as maligned as Digg was, it was still the place you went when you wanted to know what Wired articles were worth reading. What was going on with Gizmodo today. What dumb political thing you could be outraged about in 3 minutes or less. It wasn't the place for people who lacked the attention span for Twitter.
Digg did not improve Reddit but it didn't drag it into the sewer the way 4chan did.