I try to avoid spoilers when reviewing, but not this time so watch out. Also, I put off watching S2 because the ending was spoiled for me, but I finally got around to it.

Problems with S2:
-Everything felt rushed and fast-paced in places because it was only 6 episodes. I would have liked to see more, but I don't want to go through another season of JJ being confused by her own feelings again. It gets old.
-SO gets treated like HY in S1: you barely see him, and when you do, he's upset because JJ is in a relationship
-JJ's communication issues are worse now. HY is now her boyfriend, but she doesn't tell him about the shield. She just lets him think he's in a one-sided relationship, and it's really sad to watch. Whenever he rings her alarm, I just feel bad for him.
-The afterthought that is Brian Cheon and the whole Ringing World subplot. I didn't care for it. Focus on the romance or focus on the moral implications of Love Alarm. You can't develop both in just 6 episodes.
-Spear: Why tf couldn't he just take off the shield? I know the spear represents her autonomy/her ability to chose the ONE she loves instead of having technology tell her EVERYONE she loves/could love, but still. I guess a plot device will always just be a plot device.

About the endgame relationship:
Rewatching the first season before starting this, knowing she'll end up with HY, really changed my perception of S1 and her relationship with SO. It was so toxic, the only reason I rooted for them was because Song Kang is so damn handsome and such a great actor. He's selfish and stalkerish throughout the whole season and he has no respect for his best friend's feelings. It's horrible. It's good that they broke up because S2 shows that they're better for it.
JJ and HY's relationship: It's still a little messed up, and kinda toxic on her part, but it's a more mature, slow burn that gets better as they go along. I loved the photo scene in the beginning. Their relationship just feels more secure and lasting than anything she had with SO.