You could, but it would be better to use it before an adjective. 'Inherently' is also mainly used when it is natural or inevitable. You could say 'The child was inherently playful', because children are naturally playful (most of the time). 'In essence' is more used like 'mainly'; it outlines the main points of something. 'In essence, it was a bad place to live' would mean that, skipping a complicated explanation, is a bad place to live. Hope I helped!