I have heaps of experience with Stencil and it works great until a certain size indeed. It is a great way to ship web components quickly.

Coding agents will allow us to write plain JS way more quickly but it still takes a bit more time by humans to read compared to reading something that was written with in a framework.

Until the day that I don't have to do reviews of my AI generated code, or some sort of pseudocode abstraction layer becomes available, I think there is still a place for frameworks and libraries to create web components like Stencil.