He certainly is developing the language in that manner, but he is rooting for a wider adoption if nothing just for vanity's sake.

I understand that Rust can be a viable replacement for some people because it has libraries available (it is pushed by a company), but languages like Jai still need a long way to go before anyone can actually use it. The crankish circumstances under which it is developed do not promise good chances of this happening.

C++ is bad regarding many things, but it is not that bad. It is mostly hated for it's complexity and letting you do anything you want. But especially if you are an independent developer, you are not forced to use things you don't want to, and language giving you full control is a positive thing (at least in my opinion) in contrast to strictness of Rust. I myself wish there is a better language, but the amount of libraries available to me and years of experience with the language make me stick to it.

Creating a new language is hard, but getting people to use it is even harder, even if it is pushed by a corporation. Blow seems to fail to understand that language adoption is not just about syntax and paradigms but also ecosystem and libraries. You need people willing to make libraries for the new language so that even more people get interested in using it for their projects. This could take a decade or more. As far as I know he is working on that language by himself, or is there a community or at least some other contributors? Blow is a guy who writes his game engines from scratch and it seems that he wants to make a language that would suit his own needs, but even if other small developers like it most of them would still need 3rd party libraries to be able to use it for their projects.

Of course, C++ isn't a "really terrible language", it is an industry language used in big projects where performance is paramount and has been around for a long time. It has a lot of flaws but people use it because it's portable and has a huge number of libraries available. You cannot just replace it with a new better language because of all the legacy code, so the C++ standard committee is trying to improve it by modernizing it, expanding the standard library and deprecating features while maintaining backward compatibility. Whether this process is going in the right direction can be questioned, though.