I’m only missing tag support on emails from them. In my ever growing archive, I came to realize, that tags are better suited for organizing than folders.

Ideally I would archive in yearly folders and also tag as much as I can.

I would say, it’s them caring about the product and their needs, rather than the underlying stack.

PairDrop is a fork of SnapDrop, which at one point had more features and active development. Don’t know, how it is nowadays though.

I can recommend you ICSx5 for ical subscription and DAVx5 for calendar synchronisation.

Yet I would agree, that a good calendar app should ship with these features.