Index size and index usage are unrelated. Modifications to the index to keep it in sync with the table do not count as "usage" - only reading it for where clause use counts.
So only those with 0 size, should be deleted? Is that you're saying?
I'm not offering advice as to when to delete or not delete any particular index.
Can you be more clear please?
Probably not :)
You cannot make an inference about an index's usage by looking at its size. Similarly, a seldom used but large index is not necessarily one you want to remove if doing so causes a once-a-month process that usually take seconds or minutes to now take hours.