> what other language needs to distribute to an unknown runtime environment over the network?

What is this unknown runtime environment? Even during the browser war, there was just an handful of browsers. And IE was the only major outlier. Checking the existence of features and polyfilling is not that complicated.

And most time, the browser is already downloading lot of images and other resources. Arguing about bundle size is very hypocritical of developers that won't blink at adding 17 analytics modules.

> Checking the existence of features and polyfilling is not that complicated.

Judging by what we see in the world, most developers don't agree with you. And neither do I. A handful of browsers, multiplied by many versions per browser in the wild (before evergreen browsers like Chrome became widespread, but even today with e.g. Safari, or enterprise users), multiplied by a sprawling API surface (dare I say it, a standard library) is not trivial. And that's not even considering browser bugs and regressions.

> very hypocritical of developers that won't blink

Not a great argument, as developers don't necessarily get to choose how to add analytics, and plenty of them try to push back against doing so.

Also, the cost of parsing and JIT'ing JS code is byte-for-byte different to the cost of decoding an image.