Disagreed. C with syntax conveniences is what most people need.
God help you if you are doing multi-threaded with closures and callbacks, web programming, something high level like ML, etc. I feel like the thesis statement of Jai starts with "Ok, so lets assume most programmers are trying to program custom game engines...". True for a very limited set of people, but makes it very painful to use generally.
Its the same feeling you get trying to use Unreal for anything except 3D first person shooters. Its possible, it just doesn't feel very good, and you start to see all the quirky assumptions of the framework.
At no point did Jon Blow make the claim that Jai would be a good language to do web development with. It is a low level system language, if you are making something that requires low level systems language features then you will probably like Jai.
If you are making custom game engines, Jai has some conveniences (especially if you don't use any libraries or care about docs, ecosystem, community, etc). And if you really like "roll your own" with a dash of "everyone thinks I'm nuts but I'm just that much smarter", its perfect. Its one step above "I wrote my own scripting language".
Hence why I say, if you are doing complex / multi-threaded code, good luck to you.
This is why the GC and memory safe languages have mostly taken over. They have even more ergonomic syntax, and none of the footguns. You can still do all the normal pointer casting / abuse type stuff in most of these languages too.
it is true you dont want to trip you up by the language you use, but look what people actually use the languages, not by theory.
almost nobody writes the high performant code directly, usually they just call some libraries that do the job instead. if you are the library writers, then sure, that's a different matter (but people have been doing it forever using c/c++), but for people who use the libraries to write the code, they don't care about any of that.
many people rather pick python, lua, ruby to write applications, even games, despite the low performance of the scripting language, but they don't care. and if it is only the scripting aspect of the whole framework (implemented in C++) then the speed lost is even less.
heck, even for rust, the core libraries always need unsafe blocks, despite they do not recommend user code to use them. it is the same story everywhere. the hard part will be write by more experienced people (and with more effort), the typical users just write domain logic instead.
so, for most people, they indeed need simpler languages with lot of syntactic sugars for better developing experiences.