Finally, it only took them 10 years to get around to updating that decades old UI. Wonder which other decade old UI parts are they gonna tackle next? ooh, will they finally do something about Library and the whole bookmarks/history menu/sidebar/window mess? It's a little insane how so much time has passed and so many versions were released, and some interface stuff still remains unpolished and disparate. Firefox simply can't get it together on that front.

For tab containers, maybe there's a "good reason" that no other browser has that feature, cause it is confusing both as a concept and in use, and doesn't separate the rest of the stuff (or even the stuff in intends to separate when it's cumbersome and peculiar to use). Like, shared history, or inability to have separate extensions, defeats many of the purposes people use profiles for - which is an actual complete separation of things.