A lot of Defedralization is already happening .....and in most cases smaller instances will defedralize with bigger instances. That is because larger instance allow anyone to sign up so this makes it harder for smaller instances to moderate and if your arbitrary metric of 99% of users "do not give a shit" stands true then there isn't really even a point to really join coz u are not taking advantage of what the fediverse really has to offer. The fact remains that it is complex , I am not making it complex nor is anyone on purpose trying to make it complex. Even if people were do do exacty as you say and only sign up on "lemmy.world or lemmy.ml" in most cases even that right now is not easy coz these instances are currently experiencing high traffic and are giving errors ...There aren't any good polished apps (at least on ios don't know about android but it is a pretty similar situation) . So all and all anyone coming from the web2.0 apps will not have the easy onboarding they previously had. You are trying to oversimplify it which goes to destroy what the fediverse is trying to build that no instance is less or more important , while you dont need to sign up for every instance in existance you should still look into go explore new instances that cater to your specific needs and interests and then consider creating an account there ...and since account can in most cases be migrated you can later on only have one account once you have found all the communities you wanted to join.