A lot of the criticism I have of this book can be waved off by saying it's just inspired by 80's video games, so let's do it this way:
Why this book is shitty, as explained by comparing it to 80's video games.

1. The narrative framework for the story is utter crap. Seriously. The rationale for why the story happens requires so much suspension of disbelief that I simply could not handle it. It is completely contrived for the sole purpose of making it possible for the book to be all about the 80's, with characters that constantly talk about stuff from the 80's even though, presumably, they're teens living thirty years from now. The story only becomes readable about one fifth in, when it relents on the incessant name-dropping and references to 80's stuff that doesn't make an iota of sense, and starts, like, telling a story. This is reasonably for an 80's video game, where you didn't really have room for story-telling, and the narrative framework could be disposed of without losing any of the fun, but then nobody remembers Space Invaders for its impressive story arc.

2. The world-building is flimsy at best. It would seem not a single bit of pop culture was created after 2010 in this book, other than the OASIS itself. There are references to things from the 1990's and 2000's (Fight Club, for example), but Cline didn't really try to create a believable world outside of his nostalgiafest. The dystopian aspects of the society he describes are also essentially "now, but worst, and with more technology". Zero creativity, zero innovation, leading to a completely unbelievable world. (Seriously, why couldn't he set this story in 2020, where it would be mildly more believabe? Mildly, but still). Now, that was OK for an 80's video game, where the world was merely a background for gameplay, but then nobody remembers Street Fighter for its innovative world design.

3. The characters are barely 2 dimensional. In fact, I'm pretty sure Mario has more depth than the protagonist of this book, and has more believable motivations for his actions.

4. However, like many 80's video games, it's quite fun if you only focus on the action, and not any of the, you know, story parts.

In conclusion - references to beloved pop culture tidbits don't make for a good story, and you can't base a book on the structure of arcade games. If it wasn't for all my friends going bananas over this book, I wouldn't have gotten past page 30. I'm not sure it was worth the effort.