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.