And that changes the game a great deal. The innards of the browser matter.
For instance, on Windows, I usually use Firefox, but I use Edge to view Netflix, as (for whatever reason) Netflix supports Edge's EME pipeline better than the other Windows browsers. That's specific to the browser's innards, not to its skin.
...and that's like slapping a custom badge on a Ford Fiesta and calling it a Ferrari.
You're other points are much more interesting though. One of my biggest gripes with the other leading browsers is they often feel "foreign" on your host OS (which isn't Windows in my case, but that is just personal preference).
No, it's like slapping a custom badge over a Ford Fiesta platform's B3, re-do completely the interior, add some smart features around it. Hell, even do some kind of smart auto-assist while you are on it.
You keep the engine and the architecture around it but add your own luxuries and niceties.
The only thing that matters is that it integrates well and is efficient on the host OS, and that it can sync settings, bookmarks, reading list and stuff between your devices.
Edge on iOS and Android will have a built-in adblocker soon.
> The only thing that matters is that it integrates well and is efficient on the host OS, and that it can sync settings, bookmarks, reading list and stuff between your devices.
In fairness, bar the "integrates well" point, any modern browser will do what you've described (where "efficient" can be used to described a number of different performance related matrix).
For instance, on Windows, I usually use Firefox, but I use Edge to view Netflix, as (for whatever reason) Netflix supports Edge's EME pipeline better than the other Windows browsers. That's specific to the browser's innards, not to its skin.
Incidentally, the DefectiveByDesign guys aren't happy about the situation - https://www.defectivebydesign.org/edge-netflix-eme