I'd go even further and say: A platform where you can share any type of media (text, pictures, video, 3d models, ...) but with threads and forum like comments as seen on lemmy or reddit. Each instance could then limit the upload size up to a certain limit or even use a decentralized type of storage like IPFS or something similar.

Also I'd love to emphasize user based moderation/curation. I'd love to have a platform where you can see everything without any censorship but there are easy ways to filter the content locally using user built presets or just a very granular configuration.

And last but not least: Single Sing On. ActivityPods is already in development so I hope all the best.