The need to incrementally change UI/UX is both a blessing and a curse, not only from a usability perspective but an aesthetic one, too. Since I use it a fair bit, I'll use Android as an example: I generally learn a new UI pretty fast, but there are still things from Holo and earlier that I miss. Also, Material Design that was mentioned in the post is a generally good thing in my opinion, but as they've tried to incorporate new widgets and things into it, its become more and more clunky to use and fugly to look at, and I personally blame incremental changes for MD 2 being shoehorned into MD 1.