Mastodon Struggles to Keep Up with Flood of Twitter Defectors

I have a few qualms with this "twitter" app:

1. For a Linux user, you can already build such a system yourself quite trivially by getting a mastodon account, joining an instance of your choosing with your acccount, and then using other things on the fediverse to have the same feed. From mobile, this Mastodon account could be accessed through built-in software.

2. It doesn't actually replace a social network. Most people I know talk among themselves or host their thoughts online somewhere, but they still talk to each other on the phone or go outside in case there are connectivity problems. This does not solve the connectivity issue.

3. It does not seem very "viral" or income-generating. I know this is premature at this point, but without charging users for the service, is it reasonable to expect to make money off of this?

Semi-related: I wonder how many of the people who joined the mass defection from Facebook a decade or so ago are back on Facebook again.