That could be said for a lot of assumptions developers make. Everyone has 32GB of ram, everyone has an SSD, everyone has an i7...
It is an old problem, but like almost everything else in computing for some reason it seems to have become much worse since about 2010.
In 2000 a developer might have been developing on a Pentium 3 with 128 MB of RAM, but they could reasonably expect their audience to be using at least a 486 with 16 MB of RAM because that was the minimum spec for IE4.
Now you're stuck with trying to impress people with a Ryzen Threadripper and 64GB of DDR5, but your webapp still has to support everyone's iPhone 7 (with 2GB to share with iOS and everything else they have running) for as long as Apple does.
Apple supports (at least security wise) probably more devices than you think.
Maybe it's a process problem, not a developer problem. Like management prioritizes a dozen analytics trackers and ad partners without any tooling for performance testing on a range of devices.
On the developer end (as a developer myself) we definitely deserve some of the blame for embracing things like Electron with such zeal in my opinion. I don't care how much memory a developer's workstation has, there's still a lot of hardware in use that can't take the bloat. I'm not saying everything has to be a native app written in vi against an original print of The C Programming Language as Brian Kernighan and Dennis Ritchie wrote it in 1978 or it's automatically shit, but something like React Native for the desktop would be far less horrible in terms of resource usage I reckon.
Or for free software, chances are it is add supported. So push as many ads and trackers until the churn rate gets too high or competitors take market share.
Or more generally, maybe the design just follows the money.
It's not the developers' job to assume anything about users. It's the project managers'.