This drama is ICONIC.. and I appreciated the first few episodes, but honestly.. what happened?

It came to a point where it switched eras then failed to explain it and I got lost and bored.
I loved the actors, they were super cute and had decent chemistry, but the writers messed up. I don't know how it got lost so easily. I have no idea why they decided to do what they did with little explanation

Nearing the end it came to my attention that somehow their whole relationship had regressed and how he hated her?
I got confused all over again.

To be honest, It was good for like.. the first half till they messed it up. Wouldn't recommend.