Thing about CD is that it's very exploration based. Using time travel, you can try to find certain machines to destroy in (I think) the Past version of each level, which will lead to modifications in the present and future versions, and a different ending if you do it in all the levels.
Due to that element, it can definitely feel slower than the others. Same with the bosses, some of them feel slower (like the one that you pretty much just have to wait for Robotnik to die) and all of them are super easy which is a bit weird.