Totally agree for the general user of the site.
For other use cases such as moderation, this is one of the most useful tools in the toolbox so while improving related topics for the general user, please be mindful of the other use cases. 
Suggest topics - next to never now.
Related topics - depends on the need as moderator. Sometimes a few times a day but for actions on sets of topics such as checking tags, closing, changing categories, seeking keywords etc. may use it about a hundred times finding similar topics.
A graphical spatial interface with colored dots based on criteria such as text, similarity rule, e.g. cosine, distance, etc.