it seems to me that the networking design is flawed. just to give a simple example: whitelisting (only seeing content of friends and followees) versus blacklisting (seeing everything ranked by an algorithm). wouldn't whitelisting already solve most of those issues? that would actually be my preferred modus anyway.

No, because that puts the effort of fighting bad actors on everyone. It means that every day you have new trolls spewing hate in your comments, and that your users have to constantly keep blocking trolls who follow them (and who recruit other trolls to join them) until they get tired and leave the platform.

This isn't an academic debate, we've been seeing this play out online for at least 30 years. Probably longer - I wasn't around for Usenet's heyday but it wasn't immune either.