Even without having seen the first 4 seasons of TAR, I think you're right. They phoned this one in.
We are watching (for the first time) the TAR that had the camel rides across the desert to find a clue. It's pretty good as the teams really have to work out the clues rather than having it handed to them on a plate. I don't remember which season Tar it is but it's the best I've watched so far. : )