I avoided watching this drama for a long time, especially because of the reviews saying how undeveloped the story is. I finally gave a chance, and it was actually enjoyable for the most part. There are more cons than pros, but it is not a bad drama and can help you pass the time.

For the plot summary, I expected some great and non-ordinary story. But, what we have is, as everyone said, nothing. The first episodes are intriguing and make you have great expectations for the future. The characters are well developed, at least in the beginning, and the world building is awesome. What could have possible gone wrong? The story goes nowhere! It's always the same thing over and over again. At the end, we have the same questions we had when starting he show. The only progress we have is the romance between Dan Oh and Haru, in which at least they have a good chemistry and are very comfortable with each other. The story forgets about the world building and mystery, and focus on the crazy love triangle and saving people from danger... all the time. We are watching Haru saving Dan Oh, or Dan Oh saving Haru. And that goes until the end. We also have a horrible second male lead that is controlling and crazy, although there is a character development for him. Great!
At the end, they still found a way to have a rushed ending.

What is good about the Extraordinary You?
- Even with the major plot flaws, the story is quite different from what we've seen so far.
- Chemistry between the leads. I liked their romance and scenes together. They were cute.
- Good supporting characters and great acting from everyone. Well, Rowoon did okay.
- Beautiful soundtrack.

The bad?
- The story goes from an interesting plot to a normal romance story of selfless acts.
- Unanswered questions, and a LOT!
- Amnesia trope. And now one, but TWO times.
- Hateful characters: the second lead (Baek Kyung) and Oh Nam Joo. I can't see how people loved Baek Kyung and actually wanted him to be with Dan Oh over Haru. I was wondering If i watched the same show. Baek Kyung was rude, controlling, toxic, aggressive, and treated Dan Oh like trash. Also, he acted that way both in and out the shadow (where we can control his action and words), so don't come with the excuse of "not being him". Oh Nam Joo was bad like Baek Kyung, but at least he was being controlled all the time, so I can give him a break.
- I felt like I've watched a show of 20 episodes, because the same situation kept repeating itself.
- Rushed ending.

To sumarize, I did enjoy watching Extraordinary You and I can totally see myself watching it again with someone in the future.
The second male lead has a good amount of screen time, ans his relationship with the FL might upset you, but he is a hopeless second lead who can't accept a no and tries to interfere with the main couple, but all in vain. Haru and Dan Oh are strong. There a lot of people who like him, so you might me one of them.
Even with the bad things mentioned, if you like romance with some angst, you might enjoy it.