It's his hobby/passion project, I really don't understand your objection.
You seem to have a problem with the fact he criticises other languages. Would you also treat someone who isn't currently designing a language with the same harshness if they also criticised a language the way Jonathan Blow does?
But he is designing a programming language. Even if it's all a fantasy or a Python script, like you claim, there's still a design.
His opinions and views on PL design are still up to scrutiny, so it's not a glass house like you claim. PL design is not compiler writing. You're free to implement all his ideas and write a Jai compiler yourself if you need a proper compiler in your hands to properly criticise the language.
And frankly, the only thing mentioned on this thread about "80% features" is not as controversial as you're making it. Nobody here is claiming it as revolutionary or game-changing, so even if you're right, your posts are a bit uncalled for.
You seem to have a problem with the fact he criticises other languages. Would you also treat someone who isn't currently designing a language with the same harshness if they also criticised a language the way Jonathan Blow does?