While I agree others may be overreacting in declaring Paperpile 'dead', to on the other hand describe ongoing development as 'active' seems hardly fitting - the changelog you linked to shows only the most minor of changes since March 2018, amounting to little more than style updates and minor bugfixes.
Communication from the developers has also been severely lacking - looking at Stefan's activity on the forum shows only one comment in May, and before that just a handful of responses to queries in February. The Android private beta was begun in November 2016, and shows no signs of being released any time soon - Stefan commented in early February that major new versions of the mobile apps were on the way, but it's now more than three months later and we are yet to hear anything further about this (ditto for the much-requested Word plugin). The brief amounts of communication we do receive from the dev team indicate development is ongoing, but the shear paucity of clear communication from them hardly instills confidence in the future of Paperpile.
I love Paperpile, and it's so far the best reference manager I've found, but the total lack of adequate communication from the development team as to what, precisely, I've bought into here is certainly making me consider searching for greener pastures - I've continued my subscription to the service on the grounds that development would continue, and we would receive the long-awaited mobile apps that were promised. But they've still not arrived, and without any indication from the developers as to what the status of the app's development is (and what their future plans are for Paperpile more broadly), it's hard to continue giving them the benefit of the doubt.
A consistent trend throughout responses to forum posts is a frustration with the lack of adequate communication from the development team, and I count myself among those who feel this way. If this doesn't change in the near future, I think it might be time to move on to another app.