The first season of the show was praised not because it had a good story or because of phenomenal acting - because it did not have either- but because the show was simply enjoyable. It was a pure, innocent, light-hearted romantic comedy. The second season, however, tries to make a 180° change and turn this into something resembling a drama. While I often laughed during the first season, during this second season I never even smiled, let alone laugh. The show wants to now rely on the story rather than an "enjoyable feeling", and it fails miserably.
Firstly, the show introduces new "turns" every episode but they end never being fully developed . Some of them are simply forgotten and never mentioned again, while others are solved in a matter of minutes.
Secondly, the pacing is terrible : small issues who could be easily solved take up 80% of the show, while big issues that could make up a drama of their own and should strongly affect our characters are simply brushed off after 2-3 minutes. A lot of things are simply left unresolved.
Thirdly, the show becomes way too melodramatic. Every single character in this show has some amazingly overdramatic backstory regarding his/her parents. Not only that but once a character's "parents storyline" has finished, it's like they completely forget what they went through and when their friend/girlfriend/boyfriend has more or less the same problem, they act like idiots, like they have never gone through something similar before. They criticize other characters for doing the exact thing they did a week ago.
Fourthly, the plot is so predictable it hurts. Everything you predict is gonna happen, will 100% happen. And lastly, the ending is terrible - all problems in the show, some of which lasted for the entirety of the 16 episodes are immediately solved with no resistance, without any explination. We are just left to assume it is magic.
To sum the story up : it was so stupid, I simply couldn't care less about what happened to the characters.
And if all of this was not bad enough, by transforming this show in a drama, you also realize how meh (to put it mildy) is the acting. You clearly feel that with the exception of Ji Soo all the actors are either idols or novices - they completely lack emotion during emotional scenes and it is very clear they are reciting a script - it isn't a tiny bit natural. The only good acting in this show comes from Ji Soo.
The soundtrack is decent.
To conclude : the show should have continued with the feeling of the first season. But it did not.