The All-Feed is very important to increase the content-quality of the threadiverse and therefore, ensure its existense. However, for smaller instances, there is only limited reason to put the All-Feed prominent in their UI, because their posts will never be present there. However, if they push people toward their the Local-Feed (which they currently do), people will only stay on their instance and overall discussion quality declines.
So, to truly overcome instance protectionism, we need a new feed, in which an instance can find a good balance between showing content from other instances and its own.
I’m on a small instance and it has local as it’s top page and then all as an option. I find the communities already subscribed to show up in all for me, I just have to be signed in. I’m pretty sure this is how all is already set up for all of the instances. Correct me if I’m wrong though, maybe I just got lucky with my small instance.