@harumkoh - there is a broader discussion about the entry of ‘Unknown’ observations that you can read here : https://forum.inaturalist.org/t/why-do-some-serious-power-users-add-so-many-unknown-observations/282
While some people believe you should leave them as ‘Unknown’ for a period of time, to me it is important to try and classify them, even if that is just into ‘Birds’, ‘Plants’ etc as quickly as possible to increase the chances any reviewers will see them as they look for records and not have to scan through large numbers of records to get to them.
Unfortunately, if they are already entered, then it just comes down to people putting in the time to do the classifications. I do have a standard text I will copy and paste encouraging what are clearly new users to try and at least enter something as an ID. How effective it is, I really have no idea.