Is it really the case they "have already learned to scale down from threads"? I'm obviously not well-versed in browser internals, but here's the very first sentence of "Threading and Tasks in Chrome":

> Chrome has a multi-process architecture and each process is heavily multi-threaded.

https://chromium.googlesource.com/chromium/src/+/master/docs...

Either way, I think browsers have a very specific scenario, where there isn't much interaction between the tabs, and they need to be well-isolated from each other. I don't think that's a good reason for everyone else to move away from threads.

Here are another examples then,

https://docs.microsoft.com/en-gb/azure-sphere/product-overvi...

https://source.android.com/devices/architecture/hal-types?hl...

https://developer.apple.com/documentation/driverkit