Are you serious? It took me 5 minutes to spin up twitter and post a shitty twit. It took me half an hour to get mastodon and i still dont know what it is, other than a distributed clone of twitter with unlimited powers given to server owners.
The threading mechanics of twitter took me a non-trivial amount of time to get my head around.
"You visit a website (or install an app) and you create an account with an email address and password" is something the average person is used to. The UX will be confusing at first - there are new concepts to learn. People will figure it out.
Even if some do, most of those will run into a tiny random roadblock and will give up.
Nothing as "techy" as Mastodon or the one you mentioned will be adopted at the scale of Twitter.