In order for that to work there needs to be effort taken to curb persistent network effect like the utterly monolithic communities on lemmy.ml. When there isn’t any, they just get bigger and stronger. That isn’t something you can do by starting new instances, it has to be done by ones with a big slice of the pie, something new instances never have unless started just after the collapse of an existing one.
Would need to be one that restricts participation of the other party, Lemmy blocks are useless in that regard. Otherwise you’re not doing anything to deal with network effect just pretending those spaces don’t exist. Something only useful for snowflakes with weak emotions, and not people who want to make a difference.