I've read some reviews while I watched this drama and of course everyone has their own tastes and their own opinion but I have to say I really love this drama a lot. It has a unique storyline,the ost is beautiful and it's even getting a Prequel. The ending is open thats true but since a prequel called "My dream the series alpha" will be released (it's delayed idk much more ) shows that there's more to the plot than you thought and maybe there will be a special episode for the present too. But you see the ending could have several ways we could interpret it and I think that's beautiful.