I could maybe see the argument in 2012 when the games were scattered to the four winds, but the first HD ReMix (aka compilation) came out in 2013 and as of 2017 everything is on PS4. They even are selling a $100 all in one package that has all the games and a preorder for 3. And it's not like there weren't recaps on YouTube.
As for the story itself, it's hardly that complex. Granted there are still some things unexplained, but considering that the games have not only justified why Sora starts every game at level 1 but also explained why Mickey wasn't wearing a shirt in KH1 even though he had one in the prequel (I'm not making that up), expecting that they won't make anything explicitly clear that isn't a sequel hook seems ridiculous. Say it's convoluted. Say it's poorly told. But confusing? Nah bruh.
As for the story itself, it's hardly that complex. Granted there are still some things unexplained, but considering that the games have not only justified why Sora starts every game at level 1 but also explained why Mickey wasn't wearing a shirt in KH1 even though he had one in the prequel (I'm not making that up), expecting that they won't make anything explicitly clear that isn't a sequel hook seems ridiculous. Say it's convoluted. Say it's poorly told. But confusing? Nah bruh.