This is just because JS is single threaded. Python has the Global Interpreter Lock, which makes it effectively single threaded too. That means you don’t have to deal with true parallelism, and critical sections, semaphores etc. It’s like Ethereum: only one thing happens at a time.

But you don’t have to parse JSON without yielding. You can make anything async by just using setTimeout once in a while. Here is one such implementation: https://www.npmjs.com/package/yieldable-json

The guy may as well have said while(1) locks up Node.

Now they get into multithreaded work-stealing, and isolates. But the solution in Node is to spin up multiple processes and pass messages between them. This is approaching the Erlang actor model, and is also shared-nothing. They even say "the schedule is a single-threaded loop per core" and "all cross-core communication occurs via the messaging subsystem".

This can also be achieved in most other single-threaded languages, too. Python with asyncio, for instance.

Tina may provide a nice opinionated implementation with bounded queues and deterministic scheduling, but those are architectural choices rather than evidence that async/await itself has failed.

Node has isolates, but it's more for sandboxing.