so what that the gameplay shares a similiar theme and formula between them? They still provide new enviornments, new characters, different situations in the story, improved UI flow and other things,
You can't reinvent the wheel without risking changing a franchise's genre and flavor too much (which are some things people are ranting about some changes, like removal of stats, spell modifiers, etc.)
overall Skyrim really isn't the exact same thing as Oblivion, Morrowind, etc. Even though say Arena I heard you can go visit any location in Tam'riel, it's graphics and presentation and other things are not the same thing.
I mean people fussing about the gameplay being similiar, is like people complaining that a fighting game series or action series or shooter series plays too similiar to each other.