You can totally use it without having Recommendations. It is an out of
the box feature of Target Standard. If you aren't seeing what you'd
expect for "Category Affinity" targeting check out this doc on how it
populates Category Affinity I've used it on all types of mboxes from
global, regional, and raw boxes and it has worked as I've expected. The
algorthm that it uses to define favorite can be confusing, so if it
isn't making sense you could reach out to CC.