Here's mainstream news trying to get people onto Mastodon, and even this is in the "tech" section: https://www.nbcnews.com/tech/mastodon-social-media-twitter-r...
That's entirely a tech problem, rather than a people problem
The common issue for all of the services are when they become mainstream. It attracts bad apples. Twitter used to be and still have some great interactions just like small subreddits do, but when a post reaches /r/all or the feed of a controversial celebrity, you know it's going to be awful.
Discord is more like IRC used to be. It thrives in small communities of 30-50 people where you talk regularly and each topic has its own channel so regular chitchat doesn't drown out the interesting bits. It's more of a daily pub talk with your friends than finding a tutorial 10 years after it was written.
It means that the network effect is still present on the site such that it is not worth it for existing users to migrate and start from zero again to a lesser known platform with low discoverability or little to no activity. Especially one with a significantly weaker network effect.
It would have to take more than just outages to damage the network effect of these social networks. Hence why alternatives like Mastodon, didn't take off as many here thought.