Disclaimer that I have read more than half of the novel. I'll try to keep this mostly about the drama but there might still be references to the novel.

Let's start with my expectations of the drama.
I expected this drama to be about a second chance at life and a second chance at the leads' love story, delving into their backstories, motivations and relationships. I also expected there to be politics, which would be interesting as the leads are already seasoned politicians and are able to easily outsmart the old officials.

What the drama is actually about.
This drama is about the female lead learning that she was stupid in her past life, and struggling to choose between the male lead and the second male lead for the whole drama. Everything that I wanted explored about the main leads was explored about the female lead and the second male lead, leaving the male lead as more of a one dimensional accessory. The politics were okay, which was frustrating as they attempted to explore deep fundamental issues but fell short.

The positive aspects of the drama.
The acting. Zhang Linghe and Zhao Jinmai are not popular for no reason. They weren't just acting, they were living in their roles. You Jinwei, Zhao Peilin, Cheng Guo and Yi Daqian were all standout roles to me. You Jinwei perfectly communicating the loneliness and isolation of the emperor. Zhao Peilin had a much less significant role but her acting as the empress was also impressive, and it truly made me sympathise with her position and actions. Cheng Guo played Shangguan Ya to the tee, expressing all of her sides well. Yi Daqian was great at showing the personality of Su Ronghua. These six actors consistently gave an amazing performance in every single scene they were in. Most other actors had amazing moments, like Chen Heyi, Liu Xuwei, Karina Zhao and Chen Siyu.
The dynamic and chemistry between the leads. They always bicker like an old married couple, yet simultaneously always act like children around each other. Their scenes are always full of dialogue, whether it's playful and humourous or emotional and transformative. They care for each other dearly and their relationship spans decades. You can't miss a single scene with the two of them in it, it will always be either entertaining, or impactful. After 2 decades, I appreciate how the leads finally learn to openly communicate with each other.
The comedy. In a drama like this, the balance between light-hearted and serious is struck using the subordinates of the leads, and although it is not new, it is hilarious. Li Rong, Pei Wenxuan, Jing Lan, Jing Mei and Tong Ye are genuinely so funny and have me smiling and laughing aloud. They really seem like one family.
Pei Wenxuan. Pei Wenxuan is the best character. He's always unconditionally supporting Li Rong in any way possible, and he's always doing the right thing and caring about others. He has high IQ and EQ and he's also passionate about protecting those he loves. Zhang Linghe conveys a masterful performance.
Relationships. Something that this drama tackles is relationships, and all of the differences kinds there are. How relationships are influenced by power, how power can be used to destroy or protect relationships. How your relationships with others affects you: the decisions you make and how you think. It's really a deep topic and I applaud this drama for tackling it and managing to handle it well enough.
Li Chuan. Li Chuan is a complex character and it's unfortunate that his complexity was only shown in the last 10 episodes. It's bittersweet to see each emperor turn into a desperate tyrant driven to the edge of a cliff one after another in a never-ending cycle oversaw by the noble families. In my opinion, Liu Xuwei is not a horrible actor, but he just feels blank most of the time. He portrays the cute younger brother well, and I was struck by his acting when he tells Shangguan Ya that Su Ronghua is dead, but other than that he's very one note.

The negative aspects of the drama.
Su Rongqing. This is one of the aspects where the title of my review is the most relevant. The director, producer and others behind this drama fail to understand what makes a second male lead compelling and worth rooting for. They have to be better in some aspects to the make lead. This makes you think that they might be a better choice. But no, Su Rongqing is not better than Pei Wenxuan in any aspects. In fact, he's worse in about every single one. This drama dedicated so much screen time to Su Rongqing, much, much more then the male lead, for what? For us to feel sorry for his tragic backstory? For us to prefer him with Li Rong? For us to like him more? It's impossible. He's insufferable every time he appears on screen. His backstory never needed to be that deep, in my opinion. He's just an insufferable rich kid who thinks that he's the best because he shares some spare change, and that means that everyone has to bow down at his feet and respect him as the living angel on Earth. In terms of his screen time and scenes, the director made many changes from the novel, which made me even more frustrated. Chen Heyi did a perfect job if the purpose of the character was to make the audience want to kill him, but the problem is the purpose of the character is to be a tragic figure that we were rooting for. Chen Heyi does not do a good job. He looks sick and pathetic all of the time, and that makes the audience hate him, not sympathise with him.
Soundtrack. It's not so important, but it can break the immersion at times. There's barely any back track for the actual leads, and instead the only memorable track is specifically for Su Rongqing.
The wasted potential of Pei Wenxuan. I hate how the drama wasted his character. Imagine if they dedicated even half of Su Rongqing's screen time to Pei Wenxuan's backstory and his own dreams, besides supporting Li Rong. He just feels left behind and forgotten about. They dumbed him down a lot from the novel, making his ideas the ideas of other people and claiming that he doesn't know things that he actually should. Additionally, there's barely any buildup about the Pei family, which could have been such an interesting plot point, added to the relationships theme of the drama, and made Pei Wenxuan a more interesting and complex character with his own dreams and drive to do what he wants, not just supporting Li Rong.
How Li Rong's character was handled. Li Rong is such a complex character and there are parts of her character that I love and parts that I hate. Overall I really like her, but I disagree with some of the liberties the production team took from the novel. They made her feelings for Su Rongqing a lot more ambiguous, to fulfill their love for Su Rongqing. If they wanted to take liberties, they should have made her love for Pei Wenxuan a lot more obvious, rather then more subtle. She's just such a complex character who tries to do the right thing and cares about the people around her, but is always perceived as being heartless.

Overall it's an enjoyable drama. The strengths are the dynamic and chemistry between the leads and the acting while the weaknesses are the highlight on the wrong characters, misunderstanding their audience and their half-hearted attempts to delve into complex concepts.