Eminem's rap style has not been left behind. Em is a versatile rapper. His rap style has evolved over time. He has tried several styles through out his career. Em started by rapping about his life struggles, then about drugs now he raps about how great he is.
He has done different rap styles but has always stayed true to rapping on issues with deep meaning, he does not rap about girls and sex like most rappers.
In kamikaze, Em called out many rappers, talked about his last album 'revival' which didn't do so well. He also talked about himself and his flaws. This is the true Eminem. Nothing has changed and I do not think anything has been left behind.