I would agree. I think the characters at the beginning are quite unlikable. But things open up a lot more as the game progresses. The characters get a lot more nuanced (Especially some of the mains. Being vague because spoilers). I think the biggest flaw in the story is that they were not able to write a compelling villain.
As mentioned above, the gameplay is pretty darn good. I usually peter out with a game at around the 10 hour mark. With Days Gone, I was happy to play it through to the end. And I ended up doing nearly all of the side quests. Contrast that with a game like RDR2 which I completed and liked as well. But I was done with the game many, many hours before the credit roll. Lots of bloat and filler in that game IMHO.
Anyway, back to Days Gone. I ended up liking it a LOT more than I thought I would.