When I switched Firefox liked to make my Macbook run hot and to trigger frequent system-wide beachballs when it wasn't foregrounded, with just a few tabs loaded. And just having it open killed my battery. This was, like, 2011 I think. Chrome didn't do these things, even with way more tabs. I'd used FF almost exclusively since it was called Phoenix, before that, though I hadn't loved and evangelized it since some time in the 2.x series.
Of course I moved to Safari after that when I realized I could gain like another 1.5-2hrs of battery life over even Chrome, and Firefox has largely replaced Chrome as the thing I use if I need something non-Safari, now.
The native browser advantage that Safari and Edge hold is real. Firefox was built in the era of desktops being dominant. I think their next priority needs to be power usage.
I'm a Phoenix adopter as well, but never left for the almost 2 decades that have passed. I do it the opposite way, Firefox is my main, but the native browser is my goto if I need something non-Firefox.
I'd like to do it your way, but there's many Firefox-only usability features that losing simply ruins the web for me.
Of course I moved to Safari after that when I realized I could gain like another 1.5-2hrs of battery life over even Chrome, and Firefox has largely replaced Chrome as the thing I use if I need something non-Safari, now.