A thing I've noticed, and I could be wrong about this, is that social networks have not done much to increase avenues for interaction between 2nd degree connect

A thing I've noticed, and I could be wrong about this, is that social networks have not done much to increase avenues for interaction between 2nd degree connections of two people (say a and b) without needing the active participation of the a and b themselves. For instance, if we have the following undirected connections: {(a,b), (b,c), (a,d)}. There could be a mechanism to make the graph more dense by the way of increasing interactions between (c,d) without needing, for example, a to like c's content for it to then appear on d's feed. Done naively, this could result in a lot of unwanted content on someone's feed, but I wonder if there are ways around it.