If we humans willingly operate by the testimony of men in all sorts of matters, then how much more should we readily embrace the testimony of God concerning the death, resurrection, ascension, and rule of His Son?
If Christ is the holiness, righteousness, salvation, truth, grace, resurrection life, eternal life, and perfection of God, then the spirit of the world is the antithesis of all those.
The creatures and the elders show us what to do now. They hit the deck, sing, and worship, so we would know what the liturgy is supposed to look and sound like.