Svelte

From APIDesign

React is dead. Long live Svelte! Svelte is new UI framework that uses observables like Knockout.js, but processes them at compile time generating efficient updates.

Weaknesses of React

The best way to learn about weaknesses of some product is to read/watch rants by competitors. Like in the following presentation:

I haven't yet seen more insults in thirty minutes talk (I could also make some when I was younger, but not as much).

Weaknesses of Svelte

In the best tradition of learning about weaknesses, let's recommend an article by a long time react user.