I think I changed my position in time.
If you are already on mastodon.social and you are a regular fediverse user , it's probably a good idea to move to another instance.
But this is for people that happen to know already the advantages of a decentralized network.
Reality is that most people not in #fediverse, don't care still, they don't get the point.
They'll understand it later on.
I think new users, in the account creation process, should land to mastodon.social or anyway a predefined default server/group of servers.
They will have the freedom to move later on, if they remain active users, if they care.
The exit door is something they don't have elsewhere.
This could be represented graphically leaving a default that's so natural to accept if you are in a hurry, like everyone trying a new thing is.
See how graphically is represented the onboarding procedure on BS.