I think rather the issue being new library popping up is more about choosing the right tool for the right project.

If you know that your project is going to be small-scaled (a MVP or POC, a blog, a UI for your home lab, a static website, etc.) then mizu and tools alike may be a good choice.

If you know that you eventually want to have thousands of customers, with hundreds of collaborators, then it might indeed be not the best fit. Going with a more "common" framework like the big name React and Vue is probably better.

Web dev nowadays offer a wide range of application, so everyone needs is different so a one-size-fits-all framework/library is almost impossible to achieve in my opinion

My personal first experience with this was Riot.js. Ultimately, I still enjoyed using it, but writing large applications in micro frameworks is hard: it feels like either the micro framework grows substantially and starts to lose its original appeal, or your application grows framework-like limbs and suddenly the appeal of using a micro-framework is somewhat diminished.

I would guess the only real way out is to always carefully constrain your scope and keep your application as simple as possible. Easier said than done...

Do you have specific reasons why this would be true of Mizu?

It's certainly possible to build sufficiently rich data handling and modularization into HTML, and to make seamless integration between HTML and components and JS.

The fact that plain HTML can be extended with custom elements already means that just about any HTML system can be decomposed so that the the most complex things are encapsulated behind components.