Plus, the fruits in the game changed all the time. In order to prevent the players from just memorizing which fruits were edible and which weren't, the players had to be good with medicine as well. If they weren't, they would die from eating the wrong fruit.
Most of the players concentrate on training their hand speed to kill these men instead of studying these fruits.
Instead of reading and researching through these fruits, they might as well train their hand speed and skills to find the best way to kill these men, since most of their enemies who knew ancient martial arts could easily be killed with weapons and machinery.
They only had to be skilled enough to get by and have luck on their side.
Look at The Dazzlings. Didn't they get rid of all their enemies just by working together?
When Jing Jie picked up a fruit and put it in his mouth, everyone was shocked.