An underappreciated failing of the smartphone age is the death of passive status indicators. It used to be that when you were on your computer, you'd set your IM client to "available", and when you got up (or if you were focusing, not in the mood to chat, whatever) you'd set it to "away".
Smartphones destroyed this by creating a world where you were never "away". Since you could respond to a message at any time from any place, status indicators no longer had the relevance they once did and faded to disuse. Even on platforms that still support them, they're usually set automatically based on activity by default and so are fundamentally untrustworthy as indicators of actual availability.
This shift was worse than we realized at the time. Of course if you were "away" or offline, people would expect that any message they'd send wouldn't get an immediate response—but the strength of this expectation also strengthened its inverse. If you were "available", that was a strong signal that you were actually up for idle chitchat. It encouraged conversation by explicitly making room for it to exist.
Today, with no reliable status indicators, there's no real way to distinguish between "this person is just fucking around and would be happy to shoot the shit", "this person is focusing on a task", and "this person is away from their computer and will only check their phone intermittently". Starting a conversation online is a complex dance of trying to figure out if you're being a bother. Social media and group chats emerged to fill the void by directing conversation to whoever's paying attention at the moment, but that unavoidably sacrifices personal one-on-one contact.
In the heyday of instant messages, I had seven or eight people I felt comfortable messaging out of the blue with whatever. Now I have... three and a half? And it makes me sad.
not to mention how it created this uncomfortable feeling of feeling like you were coming off as desperate if you responded right away
