Any large, sudden redesign is heavily disputed - that much is obvious, and for good reason, since it changes habits. Maps itself goes through continuous redesign, but each modification is "incremental" as you call it. The end result is fairly drastically changed if you look many years back, but well.... I guess it only had incremental redesign, all along the way.
I guess what I'm saying is that if reddit launches one big-bang "completely new reddit" - yeah, I agree, it's very likely to fail. But if they incrementally change it to something else, and backtrack on the bad decisions - few people will notice the radical change, they'll just remember the many small ones.