I posted some thoughts on this in my Show HN thread https://news.ycombinator.com/item?id=22844481

I'll quote it here

> My long term thoughts on aggregators for fediverses:

I think aggregation/curation sites (like pixelfed.club) can be a decentralized complement to the fediverse. The fediverse generates the content. Aggregators, can curate the content for specific topics and help new users discover content. Anyone can start a fediverse instance, and anyone can start a aggregation/curation instance.