There are ways to slim it down, but WebRTC and video playback would probably be one of the first things I'd remove if I were looking to do that!
The other obvious target is the JS engine. IIRC V8 is 90mb just by itself. I don't think SpiderMonkey is quite so large but definitely still in the 10s of megabytes. A slower simpler JS engine (QuickJS, hermes, etc) could be quite a bit smaller.
That however would limit the browser to small audiences. Many users won't accept movies not playing and many sites require a JavaScript engine with all those optimisations, even SpiderMonkey loses too much in that space.
Binary size however is less of an issue for most users.
Yeah, I think these kind of setups don't make much sense for the main "browser application that end-users use" use case. They can make a lot of sense in the Electron "I'm wrapping a browser to use as an app framework" use case though.
The other obvious target is the JS engine. IIRC V8 is 90mb just by itself. I don't think SpiderMonkey is quite so large but definitely still in the 10s of megabytes. A slower simpler JS engine (QuickJS, hermes, etc) could be quite a bit smaller.