I just said that today on my twitter lmao I guess the sound of the rain (as a suspense music) reminds me of the cave sound. plus I find so easy to watch Train because Dark is the hardcore lvl.
I'm 25 and I watched I Heard It Through the Grapevine (young leads but the rest of the cast are older or veterans)…
Thank God someone that have watched "heard it through the grapevine"!! not only from Ahn Pan Seok PDnim but the third time that he worked with Jung Soo Joo (writer of Secret Love Affair, A Wife's Credentials as well) <3
My mister is not a romance drama ! There are many romance dramas with age difference but not my mister .
hahah so, I only watched Goblin, It's Okay, It's love, Big and Parasite from your list. Big is a "big shit", Goblin I rated badly, Parasite I think they wanted to show exactly that (and not to romanticize it) and It's Okay, at that time I watched without knowing she was a h.s student (I see now that I wasn't paying that much of attention, I took 2 years to finish it). peace.
This is obviously an actor list, not a drama one. I already created one for 2020 dramas LOL.
My only problem was regarding the title, no need to justify (can be bothersome I know). The actors that you've said, I had to read other comments to understand the context lol
It's rare for me to wait for a popular actor (about Lee Joon Gi, I never watched a drama with him, I will watch Flower of Evil now ... mostly bc of Moon Chae Won lol).
This is obviously an actor list, not a drama one. I already created one for 2020 dramas LOL.
but the title, "with their projects", for me, gives a impression that because of the actors and their projects, the year was saved. Was very strange for me lol sorry.
News 
It's rare for me to wait for a popular actor (about Lee Joon Gi, I never watched a drama with him, I will watch Flower of Evil now ... mostly bc of Moon Chae Won lol).
Anyways that was it ;)