The Real Hero & Characters' Symbolism (contains spoilers)

All the members of the Demon Hunting Team (including Yinglei & Li Lun) are the real heroes of this drama. Here is why:

Li Lun symbolizes Redemption:
His redemption was through how he had helped Zhu Yan and Zhou Yichen in killing the real enemy Wen Zongyu. Him sacrificing himself at the end when he was the most afraid and vulnerable of the ever-burning wood is his way of protecting the wilderness he loved. Hence, he is a hero who protected the demons and wilderness itself. He fulfilled his oath with Zhu Yan as great demons.

Ying Lei and Bai Jiu both of them symbolizes Braveness:
Ying Lei dying to save Bai Jiu is a form of heroism itself. His character showed the importance of brotherhood and how much he valued that brotherhood he had with Bai Jiu to the point he would be willing to save him even at the expense of his own life. Whereas, Bai Jiu's death is another form of great contribution and heroism, as it was through his braveness despite being afraid, that they were able to totally eliminate Wen Zongyu from being reincarnated. It was because of Bai Jiu that Zhu Yan and Zhou Yichen got to kill Wen Zongyu for good.

Pei Si Jing symbolizes Strength:
How she showed her strength in overcoming the fears in her heart. Her contribution is her elimination of Wen Zongyu's assistant. If she had not eliminated him, Bai Jiu wouldn't have been able to access the secret lair of where Wen Zongyu had kept the ashes for reincarnation. Hence, her contribution adds to the success of totally eliminating Wen Zongyu, as obviously the assistant was there to protect Wen Zongyu's reincarnation ashes that is why he was nowhere seen in the battlefield assisting Wen Zongyu.

Pei Si Heng symbolizes Protection:
His constant assistance and protection of his sister adds to the success why Pei Si Jing didn't suffer much while she was caught in an illusion/dream. In a way, he had contributed too.

Wen Xiao symbolizes Resilience:
Wen Xiao is a mere human who was selected because of the pureness in her heart to carry on the Baize Goddess responsibility. She is not the original Baize Goddess but a mortal who is borrowing the real Baize Goddess powers in order to fulfill the duty and responsibility passed on by Baize Token Holders. The power of the Baize Token inherently co-exist with the malicious energy, they are inseparable and the ultimate power of the Baize Token can only be activated if the malicious energy existing becomes stronger, hence, the sole purpose of the Baize is to prevent the malicious energy from becoming too over powerful and at the same time to protect the wilderness. The reason why she didn't die is because of this sole explanation itself, if she dies along with Zhao Yuanzhou then his death would be useless as there will be no one to save humanity from being demonized, the capacity to do such lies on Wen Xiao herself.

Putting the whole Baize Goddess thing aside, Wen Xiao is an essential character in the storyline. She stood as the pillar that kept the whole team together. It was through her that Zhou Yichen found the will to live in colors again, it was also through her that Zhao Yuanzhou had the will to live again and felt loved. She also served as the main key to the reason why Zhao Yuanzhou and Zhou Yichen were able to accept themselves and not hate themselves as demons, the scene when Zhao Yuanzhou comforted Zhou Yichen who had officially turned into a demon, the words he said didn't merely come from his own self alone but were from his conversation with Wen Xiao too. Not to forget how she saved Zhao Yuanzhou from almost getting killed.

One can easily regard her as a 'useless character' because she is not an overpowering character. The storyline failed to focus on her character more and she had the least development among them (I agree), however if we look at the small in-depth details about her beyond her crying scenes, only then can you be able to grasp how her character is just as important as everyone else. She had a contribution to the team in a different way that doesn't have to do with power or physical strength. She is the glue that held the group together, and the moral compass. Her character symbolizes resilience because after all that she has been through she withstood them all, she never seek revenge towards dragon princess, she could never hate Zhao Yuanzhou, she showed her will to live despite being fated to die, she tolerated 300 years of torment in sundial and she lived on in the wilderness in complete loneliness like Zhu Yan because she wanted to keep her promise to him, to protect the demons counting on her. She never had any prejudice. Her heart remained pure and untainted through it all.

Zhou Yichen symbolizes Acceptance:
He is obviously a hero in this drama too, he helped kill Wen Zongyu in the end and saved Zhao Yuanzhou too. He did many admirable and righteous things. He hated demons the most, but his prejudice slowly turned into acceptance, that in the end he now carried the duty of a great demon. He is also the one who saved Zhao Yuanzhou in the end by extracting a piece of his soul, so that he could get resurrected.

Now, if everyone is a hero what is Zhao Yuanzhou then?
Zhao Yuanzhou is the hero that embodies all these traits that each of them have. He is rather the main foundation of this storyline. He might have died in the end but that is heroism itself, not all heroes need to survive or have an outstanding fight scene to be considered as one. Being a hero is not about the amount of contribution one made.

It was because of Zhao Yuanzhou that the journey started, it was through his love for humans and wish for a peaceful and carefree life (despite the prejudice and hatred he got from all of them )that became the main foundation of the new world they had come to experience after his death. His death was significant and meaningful. He didn't die in vain but he died saving his love one and saving the people while changing the world as well.

Both him and Ying Long were righteous and extremely selfless. They shared the same fate but they also shared the same love for the world. Ying Long turned into stars to bring brightness to the dark world. Zhao Yuanzhou turned into rain to bring pureness to the world and save humanity, at the same time he changed the prejudice people had towards demons by himself all along their journey when he was alive up to the point of his death.It was Zhao Yuanzhou's big dream that started and ended the journey when it got fulfilled.