As for Finn, his character was all over the map. I don’t blame this on Boyega, because it appears to me to have been a writing problem. Some producer in a script meeting must have decided that it would be a good idea to have a black stormtrooper in the film, because that’s pretty much all he was. If the plot needed him to be scared, he was scared. If it needed him to be brave, he was brave. If the plot needed him to be reckless, he was reckless. If it needed him to get beat up by a random stormtrooper, he was overmatched and beaten up by a random stormtrooper. If it needed him to hold his own against and injure an experienced force user … well, he did that too.
That’s basically all he was, just a black stormtrooper good guy because well, that’s unique isn’t it?
Be careful with racial discussions, please. It’s really easy for that to veer off into a bad place. There’s no reason to assume Boyega was cast in the part other than they felt he was good for the role.