I'm going to go out on a limb for a second and come out in Crawford's defence here.
Flex is just a simple and straight forwards damage boost. Its not tactically complex, it doesn't do much other than add an effective +1 damage average.
There is a significant amount of simple Fighter fans who want a lack of tactical complexity. No weapon swapping, no martial dice. They're the ones who made the Champion Fighter the single most used class-subclass in the game.
It seems like Flex is designed to appeal to those simple fighter lovers. Just give them a longsword and viola.
Lets not insult people's intelligence over this; that's just gatekeeping. Flex is designed to appeal to people who want to shut off their brain and just smash things. Which is valid. Don't like it? Then don't take Flex. Its not meant for you, its meant for others.