Susanly18

I think they didn't know for sure that he is a cultivator, they just assumed he becomes someone more powerful than a human being and left to pursue a different path on his own. Mortals generally are not aware of cultivators existences, usually only the top people like kings/martial art masters may hear some rumors about cultivators. When Han Li came back after 200 years, his descendant think he was lying and used a mask to cosplay his ancestor since he looked really similar to the picture they had when he was 17-18. But Li descendant happened to be there at the time, guessed that he is may be a cultivator since Han Li showed some of his power when they was trying to fight him off thinking he was a thief.

As a big fan of the donghua and the novel, I think this live action did a pretty good job on staying faithfully to the source may be up to 70-80% which is definitely a large percentage compared to other live actions adapted from similar genre. However, I think the live action cut many scenes that actually shaped how Han Li become someone like he is right now so many people who first watch the drama may find him selfish or dull/boring, but I think if anyone want to learn more about him, his motivation, and why he seem persistent on cultivating, you can watch the donghua especially the first 10 eps. I think the donghua did a very good job on compacting all the details while still make him shine as a character, more humanly relatable, and his actions also seem more logical due to other elements in the surrounding environment. The first 10 eps has many scenes that I think if were included in the live action, people would be more understanding of Han Li character.

Moreover, the real cultivation world in the novel and donghua was more harsh and ruthless where only strength matter like everyone is competing for the resources, the upper levels see the one below as ants, etc. Han Li was not a typically super hero main character but I think his behavior is very logical and reasonable based on how the world around him was built. He will always look out for himself first and if he is 100% sure he could help and escape safely, he will. But he is not the typically guy who is going out the way to save others while putting himself in danger which is what I think set him apart from the sea of super hero main characters.

If I remember correctly in the original novel, he went back to see his family after he left the Seven Mysteries Sect but did not confront his family because at that point he has been away from the family for almost 10 years. During the time under Dr. Mo care, he sent money and letters to his family every month, but slowly he realized from the letters they sent that they seem more polite and the family feel is slowly disappearing. He asked Li fei yu to help take care of the family and when he went back, he saw his family become wealthy, his sister is getting married a wealthy student from the upper town and they seemed to live peacefully so he doesn't want to interrupt that and due to not knowing what will happen in the future, if he will make any enemies, and the different lives between mortal and people who cultivate, he silently walk away. In the donghua, they made it a little different as he saw his sister getting married, he sneaked in when there is no one and left some money, medication, and a bracelet to let them know he came back but can not meet them face to face.
After he entered the cultivation world, I think there is no time for him to went back since he was caught up in the whole fight between the 7 sect and 6 devil sects, and he just made enemy with Wang Chan who is very powerful, so he was just trying hard to stay alive while make sure no one is aware of his family existence in case they may cause harm to them. After he reached Nascent Soul stage, he went back to see them but at that time it's more than 200 years since he left so all his parents and siblings died, only people there were their descendants so he gave them some medications, and a sword made from his golden bees to protect them in cases they are in danger.

You can start watching the animation “ A mortal’s journey to immortality” from ep 63-64 to continue where the live action end.