of the essence vs crucial

of the essence and crucial both are adjectives.

Word	Noun	Adjective	Verb	Adverb
of the essence	No	Yes	No	No
crucial	No	Yes	No	No

As adjectives, of the essence and crucial are synonyms defined as:

Other synonyms of of the essence include all-important, all important, essential.

of the essence (adjective)	crucial (adjective)
of the greatest importance	of extreme importance; vital to the resolution of a crisis
	of the greatest importance
	having crucial relevance