Reviewers take note first don't judge a film before watching it and second don't judge the films on 42 year old nostalgia then the films will never live up to the expectations because you had time to create your perfect film. Thirdly if these films came out with no brand attached every film critic would give it a 9 or 10 but because they have the star wars name you expect the original trilogy reapeted. Finally watch all 3 films together if you do that you will smile the whole way through (including episode eight).
Now my actual review it's good I went to see all three films together and their were only two moments I wasn't smiling one time in episode 7 once in episode 9. Which means yes I think 8 as a standalone film is mediocre but when all films are together it becomes one of the most fun to watch.
Just enjoy the film don't get bogged down in it has to be this, go in with child like wonder and you will come out as happy as you came into the cinema.