Matrix is a relatively new open source message protocol that offers various bridges to connect to other chat/messenger services: https://matrix.org/bridges/
All my contacts are on msn.
On skype.
On myspace.
On facebook.
Now on whatsapp.
It will change.
The only things that haven't up to now are postal addresses, emails and phone numbers.
If we choose things mainly because "all my friends are on it", then no.
I don't have a fb account. I don't have whatsapp. Never had.
Yet I have a very rich social life and maintain relationship with people far away.
The tools we use are a choice.
The price we pay is different depending on that choice.
The secret is to focus on quality, not quantity, and realize a lot of FOMO is involved.
For example, if they write - in the group - that the next meeting is 3 PM next Wednesday at so-and-so, unless you happen to run into them at that specific time your chances of knowing this are slim.
Are you constantly marked as spam?
I'm still smarting, we still sometimes have problems (from a different host now) but just resend via an outlook.com address and it's fine.
So, no never had our domain marked as spam on any dbl that I've checked (but only done that sporadically).
We also had a blip with Gmail around the same time (but not the exact same time), but I reported it as a false positive and it was fixed in a few days; no problems since.
We were/are sending so few emails (<1 day average) that it's not worth me spending a couple of days trying to see through the murk of MS to fix it. We're probably not losing any revenue, just have to treat MS sent emails differently to everyone else's.
Sounds wrong to me too ;o)
There is (was?) plenty of said messengers; Trillian, Miranda, Pidgin, Adium to name a few, plus XMPP transports that could be used from any Jabber client. I've no idea though whether they're still around and play nice with modern walled gardens that require registration by phone no.