I don't think reinventing is quite right, reimplementing more like it.

Remember the thing that Microsoft was afraid of for the Web? A middle layer that makes your OS mostly irrelevant.

It took a roundabout way but we're getting there. Extremely high performance virtual machines that are all fairly compatible, are deployed across a vast range of operating systems and devices today.

Together with an UI toolkit that renders fairly similarly across all these devices.

Technically this maybe can't do things that a single computer couldn't do ages ago, but now every computer can run that code. And via LLVM you can compile almost anything to js.

And with a much better security model than "download random exe and run" as well.

The sneering merely shows that you haven't really thought about what is going on here.