I think that document is no longer very close to Jai's current state, note that it wasn't edited for quite some time and Jon seems happy to just rip stuff out and replace it wholesale, after all there's only a handful of Jai programmers so if not now then when?

In particular I believe the SOA stuff is gone, my impression (I don't have privileged access) is that SOA is one of those ideas where you think "Oh! This changes everything" and for the next week or two every time you do something you realise SOA would make it better. But a year later you find yourself unwinding some of that SOA mania and you realise eh... this isn't such a great idea that it deserves to be a key language differentiator. It's not useless but it's also not fundamental so maybe write a library or something.

There are a few other data structure tricks which can hit people this way, I remember I had a brief period where I wanted to solve everything with Bloom Filters and then I got better.

In terms of languages you can go try yourself today, the closest might be Ginger Bill's Odin. Shared scepticism for both C++ and modern language trends, syntax is reminiscent though far from identical. I'd be surprised if you hate one but love the other.

Edited: Somehow I removed "no longer" from my initial sentence during editing, which inverted the sense, now fixed.