HolyOniiSama
He did not get stronger for plot reason And even if he could not get stronger couldn't he ask his brother for a devil fruit or something.
Having a system is one of the worst idea one could have it makes all the hard work and training he did a joke Now mc has no skill no talent or creativity just a slave of good old system If he got good devil fruit from roger then it would have been much better and would make sense Well thats my opinion and u can have yours
HolyOniiSama:well, i already gave him a op system what more do you want, beside devil fruit takes away his swimming so, it isn't good compared to the system and roger travels a lot while rojen only stay in his village, roget is a pirate while rojen is not so yeah