I say this regretfully: Westworld.
Look, honestly I was into it up until the last episode. I knew the story was twisting and turning a bit too much but I kept watching and very much enjoyed the last season.
I say that it lost sight of its original premise because yes, technically it did. But that doesn’t mean the content wasn’t still great — this is a perfect example of losing your audience by not following the original narrative. I sometimes think the show would’ve been more financially successful had they dragged out the first season into several but I wouldn’t have wanted them to actually do that.