Which explains the idea much better than I ever could.
Two things had me sold on this:
1. They managed to make the thing so easy to use, that even people who's line of work involves mostly Excel sheets were able to create something useful after a short introduction.
2. The output is relatively readable JS. There are some surprises like a few one-letter method names, but overall you could open up the source of a running Svelte app(provided it weren't minified) and figure out what it's doing just by reading the code.
There's light at the end of this tunnel in the form of compilers like Svelte or Stencil.js replacing frameworks.
The improvement here is that since there's no special runtime the bundles are very small, so there isn't a lot of JS to parse.
Also the code you have to write is much shorter comparing to frameworks.