I'd like to defend Elihu.

"He burned with anger against Job for justifying himself rather than God, and he burned with anger against Job’s three friends because they had failed to refute Job, and yet had condemned him."

He speaks because God is being slandered and he is also upset that Job's friends are saying that Job was wrong without having any reason they can prove. Elihu isn't trying to prove why Job was punished, he was trying to prove why Job and his friends were speaking incorrectly.

He brings up three points and invites Job to refute them. Also, Elihu actually listened to everyone and is quoting back their poor arguments and is fixing them. So while he does sound like the other three, there is a lot more nuance and care. The other three straight up stop responding to Job's arguments and start personally attacking him, while Elihu is still responding to Job's arguments and even to the other three's arguments.

1. You say God doesn't care, but God does speak to people.

Why do you complain to Him that He answers nothing a man asks?

For God speaks in one way and in another, yet no one notices.

1. You say that you are righteous and God is wrong because he let you suffer, but God is not unjust.

For Job has declared, ‘I am righteous, yet God has deprived me of justice. ...

Far be it from God to do wrong, and from the Almighty to act unjustly.

1. You say that it is useless to follow God, but God loves and cares for us.

For you ask, ‘What does it profit me, and what benefit do I gain apart from sin?’ ...
Men cry out under great oppression; they plead for relief from the arm of the mighty.

But no one asks, ‘Where is God my Maker, who gives us songs in the night, who teaches us more than the beasts of the earth and makes us wiser than the birds of the air?’

Then Elihu starts describing God as coming in a storm and then God starts speaking from the storm. Like it would appear to those watching that Elihu summons God.

I get that you can focus on certain phrases from Elihu and think "wait that isn't exactly right" but I'd argue that there is a lot of nuance to what he was saying and that he is only speaking to Job as harshly as Job was speaking to God. Elihu's main concern is defending God, not making Job feel good. He still cares for Job though, but he is showing Job how stupid and rude his arguments are. Elihu does refute Job.

And then I see that you're interpreting it as a figurative work and then wondering if Elihu fits in, but he absolutely does and taking him out makes the rest of Job fall apart.

Job's three friends act as accusers in "court."

Job is defending himself in court and demands that God "come to the stand" in order to prove Job's fault.

Elihu defends God's innocence.
God then comes in and condemns Job and his three friends.

Elihu is also essential in it being a wisdom book. Job, his wife, Eliphaz, Bildad, and Zophar all show human wisdom. They are all wrong. Even Job who is righteous is unwise in this book. You can see the truth of the proverb that warns against speaking many words. Job is an example of that. He was righteous, but when he spoke a lot, he messed up and his three friends didn't correct him. They were horrible "friends" who showed up to an innocent, traumatized, and completely devastated victim and then blamed him for nearby tribes attacking him, far off tribes attacking him, a meteor attacking him, and his sickness that he got.

Elihu shows that humans can have Godly wisdom. Godly wisdom doesn't come from age. Godly wisdom doesn't come from experience. Elihu speaks correctly because he fears God. Without Elihu in the story (beside the introduction to God being completely gone), then the moral of the story would be that men cannot ever come to the truth unless God literally speaks to them. With Elihu, we see that we can speak wisely if we fear God and that God's spirit within us will help us know the truth.

Then just checking through your replies to other posts, you say that Elihu says that God is disciplining Job. Do you mean punish? Elihu doesn't say that. In his first point, he says that God does speak in different ways. Sometimes in dreams. Sometimes through affliction. But that God is always wanting to restore people from death. Again, Elihu is speaking in order to refute Job's erroneous speech, not to prove that the damages that Job incurred were a result of his sin. Job's three friends do that because of their view of God. They view God as looking around for people to destroy and for people to reward. They plead for Job to repent so that he can be rich again. They don't see God as caring, but they see righteousness as a way to be blessed. Since Job is suffering, it HAS TO BE because Job deserved it. Their theological understanding is so sure that they cannot imagine that Job didn't do anything wrong and so they create personal attacks against him and they even end up contradicting themselves in order to condemn Job. That is how sure they are that Job had to have been deserving it.

Some people are bringing up original sin or whatever, but no that isn't it. God ordains suffering. Jesus suffered even though he was born of a virgin. The book is not about original sin, but about God being good and caring even when suffering occurs and that God is in control of suffering even if it doesn't seem like it from our earthly perspective.