It had some flaws but it was a solid entry into the franchise. People where mad for a handful of reasons; - They think having female characters play important roles is pandering. - They think having minority characters play important roles is pandering. - They think the First Order should have suicidally jumped into the escaping ship despite them having zero reason to do so. - They think that Luke should have been the exact same person he was 30 years prior (which is incredibly ironic, given that would make him a blatant Mary Sue, a criticism often levied against Rey). - They think Luke and Anakin weren't Mary Sues but Rey is (or simply put, they are blind to pre-existing flaws in the franchise because of nostalgia). - They wanted Poe to be a Mary Sue. - They wanted Rey to turn out to be Obi-Wan's child, Luke's child, or some other fan theory heavily based on their favorite parts of the EU. This also applies to how they wanted Snoke to turn out to be some EU Sith character.
To be fair even Mark hamill didnt like how luke turned out ---
This is my sig. Don't like it, then don't look at it.