In all honesty, I actually really enjoyed TKEM. The buzz around the writer with LMHand KGE being high profile stars, I think was the cause of the "failure" of it in the eyes of many. I mean the pressure for TKEM to live up to all of the writer's previous massive successes like Goblin/Descendents/Mr. Sunshine....that's a lot of really high expectations...which means a much higher chance of failure. Not to mention, tackling time travel/parallel worlds and basically creating an entirely new world is not easy, especially trying to explain it all in 16 hours WHILE giving a story with conflict, action, romance, etc. I almost feel bad because the chance of success in the eyes of critical viewers was very limited.
The drama did start out slow and I think a lot of people from then on had their mind set that TKEM was a flop. Then proceeded to watch the rest of the drama basically searching for aspects to criticize. And I think that is one way to approach dramas by analyzing and scrutinizing anything and everything. But personally, I think that with that kind of mindset, you limited yourself to only a couple of shows that you actually like. I am not trying to discredit anyone and how they felt towards the show, however, I think a lot of the discussions centered around how bad the drama, actually deters a lot of people who would actually really enjoy the show.

Story-wise, the parallel world concept was fascinating and refreshing. I found it pretty easy to follow, but with any concept messing with time and space, it's bound to have cracks. There were plot holes(most of which I didn't even know were plot holes until I read discussion posts--so just don't read those and you will probably be better off) and areas where I wish the show would have done more in-depth. I also do think that in some episodes the story was stagnant and it wasn't doing a lot to move the plot forward, a missed opportunity to further develop the world/clarify some side stories. But if you don't focus on those aspects, they aren't bothersome and the main plot is interesting and at least for me, something new/different.

Acting: I liked KGE and LMH together, and I think that they did well with the roles. I'm definitely no expert, but I think I have around the normal person's ability to tell if the acting is stale, so for me, their portrayals were convincing and I really felt for and became invested in their characters. KKN & WDH also really delivered! I mean Jo Eun Seob and Jo Yeong were perfectly portrayed, props to WDH, I can't wait to see him in another drama. Not really a point on acting, but worth mentioning, the main thing that bugged me with the characters (not the actor's portrayal) was Tae Eul sudden switch from showing no interest and annoyance for Lee Gon and then suddenly her tough/snobby demeanor was gone. I think the writer could have made her feelings for Lee Gon melt away a lot more smoothly. Although, I don't agree with the criticism on why Lee Gon was in love with Tae Eul from the get-go. I can picture 8-year-old Lee Gon spending hours and hours holding onto the badge thinking of this mysterious savior, and pretty much becoming infatuated with the mystery girl (also, when do the falling in love process ever really "make sense" in dramas, I just enjoy the love story without questions! >∀ <)

Most of the OST playlist is still stuck in my head and while it's not the iconic Goblin OST, it's still great.

The cinematography and production is probably the least debated area because, well the millions of dollars backing the project went somewhere! Seriously, the scenes were beautiful, especially in the moments of the time stops. If anything, watch it for the visual appeals!

I never write my opinions/reviews on dramas so please forgive me if this is not super helpful/insightful, but I really wanted to do this because I hope someone will read it as realize that go into it without preformulated negativity around it, watch it and enjoy it for what it gives.