What I was getting at can be reduced to a single word — a single letter, even: C. The fact that any software is written in C (or C++) is IMHO sufficient proof that the developers care more about performance than they do about anything else.

I think that still holds even if they demonstrably do not care about performance all that much! You are quite right: current software is heavier and slower than it used to be and than it needs to be; it is also less safe and is more difficult to develop than it needs to be.

The popularity of things like Java or JavaScript is another disfunction: although they are very different from one another, they are similar in that they have poor syntax, frighteningly bad ergonomics and poor semantics. They require too much boilerplate (in very different ways) and are insufficiently expressive and powerful. They are not even as much safer as they should be, given their memory safety!

Our industry is appallingly immature.

Operating systems in the sense of kernels might still be focused on performance, but the whole GUI layer of every major OS (maybe except macOS, which might explain why most of its utility programs are still so snappy and nice to use relative to much of the competition) is full of virtual-machine languages, scripting languages, and so on. Look at Gnome—they've wrecked their performance in no small part (so far as I can tell) by integrating JavaScript so heavily into the shell, and show no signs of reversing course. The parts of the OS typical users directly interact with, and its basic GUI utility programs, are increasingly not written in C, C++, or similarly high-performance languages with tight memory and performance control, but VM languages, languages with (relatively) big, heavy runtimes, and interpreted langs.

It's bad that so many applications have given up on even halfway caring about respecting the user's computing resources, but IMO it's much worse if you can't even boot to your damn GUI desktop without a pile of JavaScript being loaded into memory.

JavaScript delenda est. It is to the 2010s as Java was to the 2000s and C was to the 1990s: unjustly popular, and a step backwards from better, deployable technologies. Its deep design flaws are obscured by its superficial design flaws.

Choosing JavaScript is a very different mistake than choosing C (it is at least memory safe, which counts for something). But it is deeply disheartening to imagine how many man-centuries (or man-millennia?) of work have gone into the ramshackle apparatus which is the JavaScript ecosystem while better ecosystems wither and starve for lack of involvement.

JavaScript delenda est.