What I think could help against instance protectionism:
A.) Better moderation tools to protect against SPAM and trash
B.) Better curation algorithm, especially for smaller instances, to smartly curate posts that are relevant to the user
C.) Better default-values for the selected feed (All instead of local), as well as for the discovery of communities (which is also currently local by default)
If B is not realized, smaller instances will have no handle against big instances flooding their user's feeds with their posts and they will switch back to local-default again.
Overall, it can be brought down to making the All-feed more attractive. In my opinion, there should only be the subscribed-feed and an all-feed with curated posts (with different sorting algorithms to chose from in the best case). Or at least these should be the main ones.
To me, the Local feed is one of the biggest strengths of Lemmy.
It allows having in the same platform a community/instance based feed (for example, Local in jlai.lu allows you to find most of the French activity in Lemmy), and at the same time, I can use "Subscribed" and/or "All" feeds to get a broader view of the Fediverse.
Without the "Local" view, Lemmy would just feel like another Reddit clone to me, where French communities would just be flooded by English-speaking communities. On Reddit, the French community actually had to create a subreddit dedicated to listing all French subreddits, just because the discoverability of non-English-speaking subreddits is just awful by default on Reddit.
And at the same time, I don't see the need for "curation algorithms". The "Subscribed" feed already fills this use case for me.
Poorly advertised is an understatement, I never heard about this within Reddit xD I always thought that it was a third-party thing.
It is indeed similar to the "Local" feed from Lemmy then. However, it doesn't have the "I'm part of a common family" feeling that I see in an instance like jlai.lu where we know that all users from the instance see the same content.
All these issues only apply to large generalized instances like lemmy.world and not smaller instances where the local feed is the curated high quality feed.
It would be IMHO better to remove the all feed and in general get away from large generalized instances that are harmful to the federation.
But why? That goes against the whole idea of federation. If no one uses the All feed you never discover other communities. You will end up with thousands of independent reddit clones.
There are many better ways to discover new communities and the all feed causes a lot of moderation issues (basically as soon as a post has enough upvotes to show up near the top of the hot sorting on all, you see loads of low effort troll posts).
But I wasn't seriously suggesting to remove it, rather that the local feed is much more useful than the all feed (on thematic instances) and thus if any feed would be removed if should be the all feed first.
I was going to say that B might not be so easy. But maybe some kind customization on the ratio of local vs external posts on some of the top posts lists. Just a random idea.