I'm surprised I haven't seen anything like that yet following the current Twitter fiasco. Mastodon is a vastly different prospect - where are the Twitter clones that people expect at a time like this?
Today, you can’t handle (or attract) a large percentage of Twitter users without tons of financing (to handle server costs until ad revenues kick up) and lots of paid or viral advertising.
The 1st 80% of the functionality is super easy and open source, it’s the last 20% of handling advertising, content moderation, content algorithms, etc. that’s more complex.