Aguero, Kane, RVN, RVP, Henry, Rooney, Drogba..etc almost all big strikers in Premier League history has their best moments against big teams and always show up and score against them.
Whenever Lukaku start scoring against them he can be classified as a top striker. So far he's a good one, that's it. Great personality but step down from the elite. You can't be entering every big match not even expecting your big 75m striker to not even score.
He's currently scoring for fun against minnows while playing a support role at best in big games, so flat track bully isn't really a wrong name. He can't be compared to the elite who are always dangerous in big games.