It started well, it was fun and engaging and it had a good starting point.
The main problem I believe is the storytelling. The notion of show not tell is completely lost on this K-drama. The last episode, with the children's play, is a true representation of that. They show us the story we just watched and include the story we just watched again. It's like saying the audience isn't smart enough to take a hint.

A lot of the plot points were too forced. Everything was conveniently placed or things conveniently happened, like FL having to enter the dating show. I didn't mind that if it continued to be fun but it wasn't.

There seemed to be no romance outside of the love triangle. Once the love triangle stopped, the romance turned into a friendship.

The most important part was the emphasis on mental health and the importance of being honest with oneself.
I believe it was mostly a story about how harmful stoicism is and its implications for our mental health and our relationships with ourselves and the ones around us. So, don't bottle it up and don't go through hardships alone. We can be trees but we're also a forest.