Jaime, Cersei, Tyrion, Denarys, Jorah, Little Finger, Arya, Sansa, Bran, Jon, Samwell, Theon, Maester Pycelle, Stannis, Devos, Melissandre all original character who have had tons of screen time are all alive.
Joffrey, Ned, Rob, Lady Stark, King Robert, Tywin, Renly, Ygritte, Mance Rader are the only ones you could call main characters that are dead now.
Yer exaggerating.
None of those are main characters except for Tyrion, and maybe Denarys, but she doesn't do anything for the last two seasons
Jaime spent most of the series in captivity and one the run, he was a subplot, Jorah is not a main character lol, arya was a subplot, I said Jon was a main character
Theon is not a main character and never was, Stannis was in the back most of the time except for the battle of black water, you can't compare his screen time to somebody like Tywin or Joffrey
Like I said they've been there the whole time, but most of the screen time was not dedicated to them