I'm looking for a romance drama without all the extra drama, for example, revenge plots/secret identities, illnesses, disabilities, and rich man poor women problems. I also don't like love triangles but if the second main lead doesn't really stand much of a chance then it's okay. Thanks in advance!

The Lover
Juunen Saki mo Kimi ni Koishite
Date - Koi to wa Donna Mono Kashira
Kekkon Dekinai Otoko

These are the only ones I could find that somewhat fit with your request..
I dont know about the others but something like, Date - Koi to wa Donna Mono Kashira, would be perfect. Ill check the others out.
My Lovely Girl - The focus is on their relationship and how they feel about each other. Nothing really intrudes. This is a mellow, smooth sailing drama without actual drama lol. Just a romance.

Noble My Love - Just a romance. Nothing takes away from their relationship. The guy is heavily possessive though, even though he had no reason to be. He's overboard sometimes, but he has his reasons.No second lead.

High-End Crush - Same, just a romance without makjang and drama. Just a guy and a girl trying to figure things out. It's definitely not boring though, and you'll laugh in this one.
Dramas I can think of that match your description:

I Hear Your Voice
Oh My Ghost
All of the Reply dramas (1997, 1994, 1988) - sure, there is a triangle, but in all of them....it becomes fairly obvious who will be the winner.
Splash Splash LOVE
Witch's Romance