RVP missed lot of chances but he covered them with winning goals. Lukaku missed lot of chances but he couldn't cover them with winning goals. That's the difference between world class and non world class striker. A world class striker who has bad game can still come out with a match winner, Lukaku can't.
Not only that, a lot of our past strikers can score top class goals. Lukaku can't because he has no technique, he relies too much on his power & pace.
RVP can score goals with poor services, Kane could become top scorer in a word cup with worse quality player around him. Lukaku only scored goals against Panama & Tunisia in a world cup but fail to step up when his team need him, even with world classs players like KDB & Hazard were behind him providing the services.