I think you're right, Unclued, and the dumbing down has been going on for quite some time now : this year really only 2 puzzles stand out, one by Shackleton and another involving atomic number answers. Carte blanche puzzles tend to be more demanding, we've not had many of those this year. One of my favourite formats, carte blanche concentric circles, has appeared hardly at all...
The use of extra/omitted/incorrect letters as a key is, as you also say, monotonous. I suspect that this is either laziness or lack of imagination; there are surely many other ways to create a key.