Lukaku is still a good player, it is just that he hasn't been able to play with a single team for too long, and he keeps on having his system adjusted all the time. This results with him starting over nearly every year, first Chelsea then inter then Chelsea then inter then Roma and so forth, he keeps changing and teams change meanwhile, managers change, tactics change, and he is not the person he used to be because of this.
When he played with Chelsea during his era of greatness Lukaku was truly like one of a number of star players who developed in the Premier League and he made Chelsea his true home leading him to victory but everything just disappeared when he suffered an injury or two and started to leave moving between teams to be loaned or even sold until in the end Lukaku had difficulty keeping up with the development of each team he followed.
It is true that changing teams with different coaches can slow down the development of a football player especially since each coach has a way of playing or a strategy that may not be easy to follow so it is natural that Lukaku is experiencing difficulties this season.
I believe that he is good at his nation because he is the same person there, and he knows what he has to do. Plus it was just one game, he could still get worse for his nation as well and I believe that he will, but not right now. We have seen him not be that before, it could happen again.
For his country Lukaku is still one of the great players and Belgium is the country that has succeeded in creating the history of Lukaku game with so many achievements even though he has not been able to win the championship trophy at least Lukaku is the key Belgian victory.
Like in yesterday match between Belgium and Estonia, they managed to win 5 - 0 and Lukaku scored 2 goals for Belgium.