Being able to use a different library with a component, instead of the component being tied to React, is the whole point.
React isn't 100x more popular because its reactivity system or any other feature is 100x better. Half the reason it's popular is network effects – too many frontend components / libraries are made React-only even though they don't need to be React-specific.
Those network effects are the trap, not the reactivity system that's as good as any other for the purpose of writing a Web Component. If you don't want to use simple and small tools like Lit.js, that's fine, but that's your choice, not a limitation of Web Components.
The point of Web Components is not to provide a blessed state management or virtual DOM implementation that will have to stay in JS stdlib forever, it's to make the components you author compatible with most / all UI libraries. For that goal, I don't know of a better solution.