What’s missing that makes them useless or annoying for you? Do you avoid them entirely, and if so, why? What would make a starter kit actually useful?
I think that either condition, though, is probably monetization; either an upsell to more layers, or a downsell to the O'Reilly book...
Having recently gone through this trying to get into React ecosystem, but avoiding the most common frameworks, `create-react-app` has docs that sort of seem like a tutorial but rapidly spirals into random advertisements, since it's pretty simple and not really a React tutorial; in-fact Meta apparently disavowed the whole thing, but it still seems to work OK.
It seems natural, incentives and open-source are tricky though, since if you're trying to simply compete rather than collaborate, it will be counterintuitive.
In fact (you mention Next.js) React itself almost immediately spirals off into advertisements for 'supporting technologies' like some of the popular React-focused frameworks.
Maybe you can read either condition as, "Oh; this part doesn't do that" or "Oh; maybe I need to read the source code to understand" or an invitation to collaborate, rather than as a design flaw.