So you can use all the zillions of existing extensions/scripts, it really only makes sense to rewrite using VimScript as the scripting language to make it faster. Then you have a built in user base.
But according to the README, the new language is syntactically incompatible with the old VimScript. So you can’t reuse those extensions, they have to be rewritten.
Yeah, I didn't notice that. If that is the case, then perhaps there is no purpose in creating a new language. Perhaps the only benefit to creating the new language could be that it might be a little easier to mechanically convert from the existing VimScript to the new style VimScript they are thinking of.