Cups are won with "moments". Leagues by relentless consistency.Sure, most of the time yes. But there will be key moments in the season where you'll need someone to step up, maybe will be Lukaku, maybe someone else or nobody, but those are the moments that define world class players.
The moments you say, thankfully we have X player.
We've proved we can produce the "moments" very recently. The consistency not so much.
As for "world class", thats a meaningless, subjective term. I'd rather have a team of merely "very good" players and win the Champions League, again.