I am a late comer to this drama. I decided to take the plunge when I heard that a third season of the show has been released without much fanfare.
While the show is entertaining, it is also a bit patchy in parts. The whole time travel, soul swapping trope is not new but it was not as prevalent as today so there is an element of originality when it was made. The show did make decent use of that device with the FL's modern spunky persona coming to the fore time and time again to create some funny moments and genre bending twists. It worked better here than the usual modern person trying to role play and blend in approach. It gave the first half of the show a distinct personality.
Having said that, the whole reason why the FL ended up in ancient time was very old school and I don't even want to hint at the overarching plot as it will give the whole story away. This bring on the other issue with this show, the show started as a rom-com and then it got melodramatic and finally moved to full on high fantasy. The show had to do this to bring the current show to some form of conclusion but open ended enough to set up the next season. The problem is that the second half of the show felt very tropey and predictable. The production value seemed to drop as well when they moved to the fantasy land.
I will definitely watch the next two seasons as the chemistry of the CP is great and the show is built upon and carried by their relationship so if you ship them then you will want to find out what happens next.