I think you're over-simplifying the amount of diversity present in individual Kingdom Rush levels. While the first two titles were quite similar in general gameplay, the diversity in tactics you need for each level and challenges that you face in each level are actually what you qualify as entire games to themselves. Kingdom Rush isn't afraid to throw enemies and bosses at you that completely twist up the gameplay mechanics in the game, and the video trailer from Origins to me looks like it has a lot more going on than normal. I expect lots of new mechanics in the gameplay of the levels themselves from it. Just because part of it is the same isn't bad, and while the rotate your towers in a circle-thing in Sleep Attack is novel sounding, is the rest of the game as rewarding and well designed as Kingdom Rush? Getting all the achievements and clearing the game on the hardest settings in Kingdom Rush takes a good amount of strategy, and is quite enjoyable. The product as a whole is pretty diverse too, and I wouldn't really describe it as a grind or tedious. Really the sheer amount of ways it mixes up the gameplay with all the different modes is nothing to glaze by, you have the typical build up your forces mode, but then extra modes for each level where you start with a set amount of resources, or where you can't lose a single heart.
Also, Sleep Attack doesn't really look to push the bar quite as much as a few other tower defense games I've played in the past, there's some of them that are barely mentioned here which switch up a whole lot more than just a rotating battlefield... still, I enjoy new ideas, but I certainly won't be dismissing proven ones just because I enjoyed them before.
