Why can’t we have federated identity to login into fediverse instead of creating login for each instance?
True, but changing this is unfortunately unfeasible with the way the web works. If I just access the URL of a post on instance A, there is no reasonable way for it to know that my home instance is B.
There should at least be a button or something that sends you to your home instance after entering the domain though. Other than that, we’ll have to keep using browser addons and userscripts…