Google and Mozilla seem considerably less concerned about efficiency than Apple and Microsoft are. Safari is well known for being easier on the battery than Chrome and Firefox are on macOS, and pre-Chromium Edge had similar efficiency margins over Chrome and Firefox on Windows. I’ve heard that even Chromium-Edge tends to outperform its competitors on Windows even now.
This starts to make sense when you consider that for Apple and Microsoft, end users are the customer and bad battery life is going to have implications on number of devices sold. For Chrome and a lesser extent Firefox, the “customer” is instead web devs, who are more interested in a constant stream of new features than they are efficiency.
That said, both browser vendors and site devs are responsible. It doesn’t matter how optimized the browser is if a site loads tens of megabytes of dependencies and is written with expediency and cheapness in mind only.
This starts to make sense when you consider that for Apple and Microsoft, end users are the customer and bad battery life is going to have implications on number of devices sold. For Chrome and a lesser extent Firefox, the “customer” is instead web devs, who are more interested in a constant stream of new features than they are efficiency.
That said, both browser vendors and site devs are responsible. It doesn’t matter how optimized the browser is if a site loads tens of megabytes of dependencies and is written with expediency and cheapness in mind only.