I did Facebook and Reddit for just over a decade before I decided it wasn't helping me. I quit them both and went without social media for two years. I did have a LinkedIn the same way your brother uses it, but I had no social media apps on my phone, and logged intro LI once a week. What broke it was I started a job at a startup requiring a lot more involvement on socials. Instead of Facebook, it was Twitter, LinkedIn, with a splash of Reddit.
I absolutely hated it, but loved every other aspect about the job. So I got sucked back in despite an intense desire not to. I have since abandoned Xitter and have moved on to a small server with a group of concentrated folks in the area I want to build out.
I know Mastodon may seem like a distributed version of the same thing but I think the main problem was centralization and that informed design that altered our sense of self-worth and reality. Likes and followers became a quantifiable measure of our self-worth and misinformation was pushed based on whoever drove the highest price for that company. With Mastodon, there's no company, you can even set up your own and live on it as you have. Likes and boosts aren't inputs to a shareholder-driven algorithm, a like is simply a signal to the creator of the content that their post the was good. Mastodon, by being a bunch of distributed servers, makes it difficult to see stats across servers. And that's a feature mostly, not a bug.
That said, I feel like being on Mastodon has brought me back to the same level of peace and mental health I was when I had quit social media. I am 100% diving into the open web and I could care less if it becomes plate or not. My goal will not be to improve the quantity of viewers, but the quality of interactions we have.
Great post, I feel a lot of my own experience with big social media is reflected here.
For better or for worse I think I'm stuck on LinkedIn until I retire. Maybe that's the next Fedi app that needs to happen. Basically it just needs to be Mastodon with a plugin that has the same profile layout as LinkedIn.