Really great post, Ruth!
I’ve noticed a lot of the behaviours you’ve noted in your reflection in my own experiences with these types of websites/platforms – there’s not a lot of opportunity or interest by users in expanding beyond what they know or are comfortable with. As you mention, a lot of these websites make recommendations based on algorithms and other similar tools and they lack any ability to make suggestions outside of a user’s comfort zone and I think the point you make about librarians getting involved with these tools is critical – they have both the ability and the training to extend on these services in a really positive, productive way that has not yet been fully realised.