I don't think Days Gone is that bad. The IGN review says things like the map is empty and every place looks the same, but the ACG review says he likes the details that distinguishes each place (paraphrased). And the COGconneted review below actually praises the emptiness of the map. IGN complains about the story but ACG likes the story and how it's told. IGN complains about repetitive missions, no other review mention anything. IGN complains about the bike being fragile, others are ok with it, after a couple of upgrades.
The only common complaint is the bugs, Easy Allies lists quite a lot near the end of their review, they sounded annoying but nothing major really. Jim Sterling mentioned quite a few of the bugs too at the end of his review (below), saying there's a lot to complain about and it took a few hours before he genuinely enjoyed the game. Generally everyone seems to think the game is still very playable, but needs more polish that other first party exclusives had.