> .. I still believe that ranking/recommendation models should be open.
Today, we don't know how social media recommend posts to us, we don't know if it is biased, or good for some sub communities. There are [1] some engineering blogs where we can see that is based on some research ideas (e.g. embeddings) are prune to bias [3] and "rich gets richer" phenomena. There should be an open marketplace where institutes/researchers submit open & explainable ranking/recommender systems. This is how you democratize access to such social platforms, but the business model opposes such idea to make it reality. There is a large body of research in the area of explainable recommendation systems/Explainable AI. There are regulations today to use Explainable AI systems in healthcare field, but few of them in areas that impact our mental health (e.g. the use of Social Media).
[1]: https://ai.facebook.com/blog/powered-by-ai-instagrams-explor...
[2]: Explainable Recommendation: A Survey and New Perspective, https://arxiv.org/abs/1804.11192
[3]: https://aclanthology.org/P19-1162v2.pdf