His knowledge is limited to an extremely tiny domain of programming, and he regularly berates people for not following his philosophy. Meanwhile, it took him eight years to make The Witness. What did he build with his eight years time? A first person puzzle game with essentially no interactive physics, no character animations, and no NPC's to interact with. (I actually enjoy The Witness, fwiw.) The vast majority of developers do not have the budget to spend eight years on a single title, and wouldn't want to even if they did.
The most notable thing about Jonathan Blow is how condescending he is.
He's passionate and smart and interesting - and writing him off like that, I think, is not justified.
The thing about Jonathan Blow is that for a lot of people, he's the first graphics-focused outspoken programmer that they run into and so they think he's some form of singular genius. He isn't.