Complex sentence: This is the true meaning of the usage of this phrase to downgrade any entity or concept that seems to be great by recalling that "God is (still) greater" than any real entity or imaginary concept you may appreciate.
Split into simpler sentences: This is the true meaning in the usage of this phrase as to downgrade any entity or concept that seems to be great by recalling that "God is (still) greater". It is used to emphasize that God is greater than any real entity or imaginary concept you may appreciate.