These are big technical issues IMO, especially considering the large amount of tankies on Lemmy. It doesn't help that many tankies have accounts on LW and other "normal" instances.

PieFed, and the Lemmy apps Sync and Connect, can do that. They truly block users from any custom instance of your choice, without having to depend upon an admin (or spin up an instance yourself).

Base Lemmy cannot and a look at the admin practices present on the devs own instance convinces me that it likely never will - it seems simply not a priority for them (and we are on their platform - or rather you are:-).

Nothing is perfect ofc, but it's nice to have choices.