>>38248926I'd say about half of the hate comes from lumping it in with gen 6 hate as a whole which is a bit of an overreaction; gen 6 is definitely worse than generations before it but people act like the games are unplayable like Sun and Moon. They're not good, but they're okay.
The other half of the hate comes from the fact that they're genuinely bad remakes because the only things they have over Ruby and Sapphire are the Physical/Special split (which is a given), online (also a given), and DexNav. On top of that, they excluded the Battle Frontier, which was the best endgame content in the series.
That being said, they DID make an attempt in terms of the endgame content with the mystery isles, searching for legendaries, and the island the generic battle tower is at. It's still not a GREAT endgame, but it's leaps and bounds better than SM/USUM.
tl;dr
They get hate because they're bad games, but they're not as bad as people say. But still bad.