I do not agree.
Aquaman didn't have a 50/50 and he was winning plenty of majors/locals.
Doomsday doesn't have one, and he's placed quite a bit.
Raven didn't have one, and she made top 8 at KiT.
Sinestro does, but that's not all that Sinestro uses in a match up.
Batman has a situational 50/50, but most Batman players don't use it, and he's placed/won plenty of majors.
Zod primarily zones, and he's placed. He has mix-ups, but I don't think he has a true, unseeable 50/50. (Dave/Pig can correct me on this.)
If the 50/50 was as strong as the narrative implies, why didn't Killer Frost do more? Her ENTIRE deal, just like Batgirl, is the 50/50 and she controls space very well.
The Flash does have plenty of 50/50s, but he has to play EVERYONE ELSE'S GAME first, before he can come in and start his. He's a very footsie intensive character. Superman is another one with a situational guessing game, but primarily wins with footsies/counterzoning/conditioning. He, like Batman, is a very solid character.
I don't buy the narrative.