Regardless of whatever it did or however it did it, the way Pocket was suddenly shoved in everyone's faces by default definitely left a bad taste in a lot of mouths (including mine) and everybody just considered it more unasked-for adware. Especially since in its default configuration about a quarter of what it serves you is indeed flat out ads, when most of us are using Firefox with uBlock or similar specifically not to see ads.

Pocket provided a feature I suspect few people actually used, and in the process had an obnoxious presentation that a lot of people actively disliked. Add me to the list of people who won't be sad to see it go.

I want my browser developer developing browsers, not other ancillary side projects and certainly not "curating content" or whatever the fuck.

I would not be at all surprised to learn that Pocket costs Mozilla a nontrivial amount of money and manpower to maintain, what with doing all that curation and all, and provides them bupkis in return.