I don't think they're manipulating people, and I don't think they're doing this for attention. I think they genuinely didn't like how the game ended. Now whether I agree with them, and whether I think they're overreacting is another matter. But I do believe they genuinely feel that way.
Based on the leaker's twitter replies, they thought all the disney worlds up till the last one were "amazing". Then apparently the story had some ups and downs, and some crazy cool stuff happened. He says what made him say the game was meh is that they touch on some really coop things that they then just never bring up again. I can't know if I'll agree, but it's understandable. This makes way more sense than what he said before about something from the mobile game being involved that he didn't like.