Well. What makes someone a Genius?
Some people have talent with something but that is not enough to be a Genius really.
Example: Someone has the talent to never fail to dunk a ball. Great aim and talent. But, if he doesnt work under pressure, speed or other thing they cant be called a good player therefore a genius. Why genius? Because he took his talents and limits to be the best version of himself.
Michael Jordan failed many times before being called a genius.
Gai is a Genius? He discover his limits therefore explode his strengths.
Like, c'mon, Sakura is not the only ninja to ever have good chakra control yet she did become one of the best medical ninja.
She does have more potential but that is not the problems.
She is a genius but not as Tsunade in my opinion regarding to improving the medical standards.