Mastodon hit 10M users
After about 6 months hosting my own little private Mastodon instance, I can say the following things:(1) Whoever cares about that but the atmosphere is nice, cozy, exciting and creative. Zero toxicity and probably several magnitudes more meaningful conversations with people from all around the world. This apparently comes from the kinds of people I could find and connect with.(2) Hosting is relatively easy. I think all kinds of organizations (e.g. sports clubs, media companies, private companies, schools, political parties, gov't agencies, etc.) should give it a shot hosting their own instances to take control of their social media identity. 
They don't necessarily need to open registrations for everyone and start moderating "the masses". I only let few hand-picked people on my instance that I happen to know IRL and still have a happy life.(3) I once saw a post from a German IT mag (heise, I think from November 2022) that claimed that they have more traffic through Mastodon than through any other Social Media thingy. Surely, their audience was a good fit but I think it's a matter of critical mass when more less-nerdy people would join the Fediverse.In summary, I deleted my Twitter account ~2 months ago and don't regret it. Some things are a bit annoying (mostly bugs, finding and connecting with other people, not much interaction with my posts [maybe it's because my posts are sh*t]) but all in all it's a great resource for inspiration and digital interaction with other people.