The audacity’s “noise removal” can only be successful where the noise is constant throughout the recording, like a hiss artefact. So it can’t remove (say) other voices speaking at same time as your interviewee.
If you read the audacityteam.org page on noise removal then you’ll know all there is to know on the subject … Missing features - Audacity Support
If by “depth” you mean the recordings lack bass there is “bassboost” in the “Effect” menu you could try.
Or if by “depth” you mean stereo image, you could try Steve’s pseudostero plugin, which makes mono sound like stereo.