Why do you see gravity (contraction) and Dark energy (expansive) as two different things? Aren’t they just two sides of the same coin? For example, instead of saying the milky way and andromeda galaxy are gravitational bound together couldn’t we also say that they have more dark energy around them pushing them together than there is dark energy between them. Or an apple is attracted to the earth because there is more dark energy surrounding them pushing them together than there is dark energy between them. You can picture it as the universe is a crumpled-up piece of paper unfolding. Places where the folds face each other we get galaxy clusters and places where the folds face away from each other we get vast voids of space where dark energy prevails.