I think svelte compiling to native javascript is lightyears more understandable than whatever the hell react is doing
Being JavaScript?
That said, React's mental model is so powerful that I've almost never needed to actually debug into it to see what's going on. If you've got an issue, tracing the dataflow in your own code is generally sufficient. So, I'm okay treating it as a black box.
(Hiya, Shados!)