Are we really discussing Widowmaker's viability on koth compared to 76 lol?
She's awful there unless you grossly outskill the enemy team, her best maps are Hollywood, Eichenwald and Anubis offense etc, Gibraltar offense is great for her too.
Basically maps with high ground where she can get important picks which let you roll through the rest of the game, she's exceptionally on koth because it's constant team fighting which is her weakness.