Condensing the entire community experience into an app doesn't work well. It's unwieldy for people staring at small screens, using big fingers, in a moving vehicle.
Facebook is countering this with single-function apps.
They're creating separate apps for popular activities and forcing members to use them.
This means the entire app experience serves a single function. It's simple and removes the distraction. Most importantly, it uses the power of push notifications to build habits.
Most apps offer notifications. Which means we ignore most apps.
This is because most notifications from our apps are of low interest to us. I have 74 unread SMS on my phone right now. The majority are automated reminders. I have dozens from various other apps. Most are automated, unimportant, reminders or nudges. So we ignore them.
Yet notifications from single function apps, like messenger, are hard to ignore. On messenger we know it's a friend talking directly to us.
Single function apps are more important to communities with 100k+ members than 10k. For the few communities above that level, it's a powerful tool.