People forget that Firefox gave the world tabbed browsing. Sure, it was around before, but Firefox was the drive and impetus that moved it from a niche idea to the default option across every browser. That was over a decade ago.
Firefox has the opportunity to execute a vision of modern web-browsing again. And, frankly, we really need it. Tabs use to be the solution; now I measure problem difficulty in terms of tabs I have open ("That was a 10-tab problem"), and find myself closing 15-20 at a time.
Arguably, Pocket is trying to do that, but as a secondary service. It needs to be integrated, and seamless. I want stacks of tabs, tagged tab groups, an Inbox-like interface for my web history, including reminders (rip Inbox Reminders), predictive new-tab screens, cross-device tab sharing. I want to collect and link sites I've seen, and quickly be able to find them again. I want internet history that's a set, not a random list.
Firefox could bring us the next wave of web browsing again. Instead, they're building an app that claims to make web browsing better---by going to a second location.