It amounts to a bad remake of the original; Leia and Han leading the Rebellion against Imperials ruled by the Dark Side with Luke a Kenobi/Yoda blend, Kylo just another Anakin/Vader, and Rey a Luke figure right down to hearing Force voices & growing up on a destitute desert planet & saving BB-8 (the R2D2 equivalent with vital information that is hunted by Stormtroopers who themselves want to keep it from the rebels).
The Sequel Trilogy – as any worthwhile sequel – was supposed to be original, a new generation of Jedi trying to put the Republic back together and facing new, more unique, enemies in the process. I can see why Lucus and Hamill think little of it.
If this "was supposed to be" line sounds arrogant on my part, it is only because I hold Star Wars to the same standards as any work of literature. If a brilliant author writes something that is an inferior copy of the original – yes, David Eddings, I am referring to your The Mallorean and The Tamuli – then I do not read it. At this point it must be noted that the original Fantasy series' that preceded the aforesaid ones, Eddings' The Belgariad and The Elenium, are easily some of the most entertaining books I have ever read. I am not a laugh-out-loud sort of reader usually, yet these had be consistently howling. (Both are five-volume works, however, so if you have to choose then I recommend The Belgariad.)