I watched this months ago so on one hand I don't remember too many specifics, but on the other hand, what you remember about a drama months later can really reflect how good or memorable it actually was. So here's what I remember liking:

1) Crude Play. I loved the fictional band in The Liar and His Lover. I loved their friendship and the storyline about their struggle with their company. I also liked their songs and listened to them on Spotify for weeks after the show. They're still on my playlist. (Also, Kim Sung Joo plays the lead singer, which led me to discover his kpop/cpop group UNIQ.)

2) Shi Hyun (the aforementioned Kim Sung Joo) and Soo Yeon's storyline is SO CUTE and I have rewatched their clips on YouTube before.

3) I recall liking Yoo Na's storyline a lot. It was very emotional and I thought Hong Seo Young did a great job.

4) Most disappointing was the leads and their relationship. So Rim (Joy's character) was kind of silly and foolish, and Han Kyeol (Lee Hyun Woo) was a dummy. And then you had to feel bad for poor Chan Yeong because he was totally talented and deserved a chance to succeed.

So I wouldn't say this drama is a waste of time - I would totally watch the Crude Play and Shi Hyun/Soo Yeon parts again.