That's been the case for just about every Gamebryo/Creation Engine/Todd Howard game. TES4 and everything after kinda blurs into the same slop for me. I remember people saying F3 was 'Oblivion with guns', and Skyrim was 'Fallout with swords', and having played all those for hundreds of hours, those statements aren't wrong.
Halfway through my second playthrough of Fallout 4, I realized that I had been playing (more or less) the same game for 10 years. Same gameplay loop, more shallow characters, and more mediocre writing, and to top it all off, I wasn't enjoying the open world/sandbox all that much. Not to mention, all of them have the same weird kinds of bugs and crashes. I decided that until Bethesda starts writing games properly (story- and code-wise), I'm going to pass.