Epic didn’t pick, the game was in development long before overwatch was even a dream. There is gameplay of it from 2011. They had lots of time to get things right and make sure it was a complete game. Overwatch though, I feel they did a much better job in a much shorter time when it comes to quality, which sort of reinforces your point, I guess.
Note: I actively play Fortnite save the world (pve version) the famous Battle Royale and over watch.
All game studios get warped when a game gets popular. Naturally they will throw all their resources at a popular game, which epic did when BR got huge. Overwatch was never Blizz s top game, so this game never got the special treatment.