The Platform - One of the best movies I've seen in years. The Director have said that he left the plot and the ending up to interpretations, after reviewing multiple theories and reviews online, here is what I believe is the correct conclusion, spoiler alert obviously.

The Hero: Goreng is a student pursing his degree entering the capitalist system (Rat race) voluntarily but he finds it hard to adapt to a system that lacks any values, works on changing something.

Trimagasi the old man is basically Goreng's evil in his head and he represents greed as well.

The interviewer, imoguiri and her dog represents communism in theory and on paper only, not applied communism, she's the cancer inside the capitalism (Literally) she voluntarily joined the hole, while the head of the system never gave accurate information about the hole to her.

When Goreng wanted to help the communist to apply communism he did it by force, probably hinting that communism can't be applied without force and a dictatorship (China as an example)

Miharu the Mother, is Mother Nature, she's nature in normal operation, we see her killing some people with no reason we see her helping others.
She doesn't have a child (I'll explain below)
She suffocate because of the system as well.

Baharat is a religious man, he means and intends good but he is blinded his beliefs which gives him so much shit (Literally) in life, the wise man that he meets on the way down is religion.

The chief is the head of the capitalist system.

The child at the last floor 333 is only Goreng's imagination, the child looked 4-6 old and time you spend in hole makes this impossible to happen even if she was born inside, her survival is not logical.
The mother only represents nature (No father, no child as mentioned subtly)

Ending plot:
The child never ate the Panna Cotta, the dish that was supposed to be sent up to the head of the syetem as a message was actually sent.
However the management misunderstood the message

A very important scene is where the head of chiefs scolds the cooks for having one hair inside the Panna Cotta, I believe this scene happened after the dish was sent, means the message was misunderstood.

No matter how hard you try people on the higher levels of hierarchy will never understand the struggle and needs of the people beneath them (Literally)

Goreng's book is a Spanish novel (Don Quixote) about a man who lived & died thinking that he succeeded in his sacrifice but he didn't. Which pushes me more to believe that Goreng faced the same ending, dead and its a hopeless case, the message was never helpful to change anything