Like any other written work, comics are a reflection of their author, the author's views, and society. Combine that with the ability of newspapers to pick and choose the comics that reflect their readers' interests, and it's natural to see change over time. Also, while the characters in comic strips are ageless, their authors do age and change, and this shows up in the panels in subtle ways.
Sally Forth is one of a number of comics whose authors have gotten so deep into naval-gazing and re-hashing the same old story lines year after year that they're in a death spiral. For SF, in particular, it seems to have gone off the rails about five years ago. It's neither funny, nor insightful. It's just a lot of words words words with little actual content.
I never understood Prince Valiant. Maybe once a month I'll look at it to see if the story is at a point where I can jump in, but I never know what's going on.
Dilbert got stale, and its author fell into the naval-gazing death spiral, too. See also: Crankshaft, Luann, and Candorville.
Garfield is boring, but it always was. For better or worse, it remains light entertainment, and there's nothing wrong with that.
Schultz died, and what you see now are re-runs of his old strips. In some newspapers, the title has been changed to Best of Peanuts, or Classic Peanuts. But some just kept the title Peanuts.
I don't think there could be a modern version of Calvin and Hobbes. Society has become too touchy. Too angry. Too opinionated. Too closed-minded. If anyone tried to re-capture what once was C&H, they'd be pilloried on social media for imaginary crimes. See also: Bloom County. Red & Rover could be a contender, but it's more nostalgic than clever.
For Better or Worse has been in reruns for a very long time. Its content has always been so milquetoast that I didn't even notice it until you brought it up just now.
Also in a death spiral: Ziggy. Same three gags over and over. Breaking Cat News. Zits.
B.C. is also the same gags over and over, but somehow it's not so bad. At least it's not angry.
Get Fuzzy is good, though it's still sometimes strange. Also, Pearls Before Swine. They're only good, but still the best strips out there. Donesberry has mellowed out, and is more readable than it has been in a long time.
I don't think there are any "great" strips anymore. But looking through my Sunday papers today, these are ones I find OK: Baby Blues, Hi & Lois, Baldo, F Minus, Wumo, Rhymes with Orange, Mutts, Argyle Sweater, Drabble, Mother Goose and Grimm, Pickles, The Brilliant Mind of Edison Lee.
Somehow I still find Blondie and Hagar delightful, and it sometimes manages to work in new topics.
The problem with comic strips is the same problem that all of comedy has: Society is ruining comedy. Big-name comedians like Seinfeld will tell you that it's just not fun anymore. People go from zero to machine gun in the time it takes to spit out one joke. Nobody has any sense of humor anymore. Everyone has to be offended about everything, or they don't know they exist. Can you imagine what would happen if some of the first or second season of SNL were re-aired on NBC, or one of the Dean Martin TV roasts? People would burn down the Comcast building. Can you imagine Richard Prior or Red Foxx doing a set on a college campus? Mass hysteria.
People need to get over themselves. They've forgotten "Sticks and stones may break my bones, but names will never hurt me."
