The first six episodes of Serendipity's Embrace were a light, tropey, rom-com that used a number of interlocking story lines to offer a number of different takes on the mark that your "first love" can make on your life--traditional stuff. I'd even call episodes 5-6 quite good as these things go.

However (하지만), I'm not sure I've ever encountered so many (attempts at) a series of happy endings each of which are compromised and distinctly unsatisfying.

Lacklustre. Everything was lacklustre, but especially the end. I couldn't bring myself to care by episode 8, and I'm not sure any of the cast could by the end. A valiant effort from KSH, but even she couldn't bring the magic. If you're totally bored with ironing, stick it on?

I liked the first 4 episodes but after this I felt there were so many storylines but yet all of them underdeveloped to the point I didn't really care about the characters.

Mostly, I blame the director for this as the high school scenes were placed as an afterthought and all too often the FM went "ah, now I remember", but as the past showed, they spent a HUGE amount of time together and seemed too close for the present time interaction to make sense.

Nice initial episodes but an ending that left us frustrated. It gives me Heartbeat vibes in terms of unsatisfying and annoying ending.
https://kdramadiary.com/kdrama-review/serendipitys-embrace-tvn/

Thanks to all the beanies takes on it, I won't feel bad about dropping it at episode 5.

The core of this drama seems to be the flashbacks to high school. The ML remembers all the interactions he had with the FL good and bad with a loving eye. It is like a love letter to her, which ironically contrasts with one part of the story. I don't find the FL appealing. So, this didn't work for me. I dropped it after 3.

Sweet but soon to be forgotten; this reminded me of Our Beloved Summer lite. Kim So-hyun did well playing the same character she always does in her rom-coms, and Chae Jong-hyeop was a more boring/stoic version of his usual charismatic-sunshine self - until his smile returned like sunshine from behind clouds. The ex and the mom soured some of the sweetness, but I fixed that by using FF. Overall, it was sweet, simple (especially when using FF), and short, like a webdrama with excellent production values.