I agree with you but I think mastadon has bigger shoes to fill.

Businesses looked at Twitter as a reliable way to communicate with a broad audience. To the point that even police services thought it was good enough.

Mastadon, if it wants to be seen as a replacement needs to be high reliability.

I don't think Lemmy has that expectation. Like there is a user in these comments complaining that we didn't get notice of down time and I'm kinda wondering why he would want that let alone expect it. As you say it's recreation and so I don't need that high level of reliability.