I don't agree with this assertion. Back in those days, most people in my friend group were using MSN Messenger. The steps to get onto that were probably easier

I don't agree with this assertion. Back in those days, most people in my friend group were using MSN Messenger. The steps to get onto that were probably easier than signing up for Facebook/Insta nowadays. The same was true for yahoo, AOL or a whole bunch of other messenger services. But these all had open protocols that clients could implement, and they did - Adium for Mac was a great example, and it worked brilliantly. The only thing missing there was an open protocol for group video calls, which is why Skype came along. If we had continued on that path of open protocols (not even standards) vs. proprietary & locked down services, we'd be in a much different place now.