Apple love to preach "the UI gets out of the way of your content" with each new redesign, but how true is that in practice? Let's compare the total height of the Safari UI with a toolbar, favourites bar and tab bar visible, across the three latest Mac OS design languages – Yosemite, Big Sur and now Tahoe. I've added a red line for emphasis.
It sure looks to me like the UI is eating more into my content with each redesign.
Integration with macOS and features like synchronization with iOS/iPhone or generating new iCloud mail addresses.
I always use other browsers in parallel. Sadly they typically fail to adhere to macOS UI conventions or don’t integrate as well across devices.
I use Waterfox (Firefox fork) as a secondary browser because of the more powerful extensions. Other than that usability and OS integration is worse.
Camino used to a be a good Mozilla/gecko browser back in day. Sadly it was abandoned a long time ago.