Who said that? But scoring 60 goals as a NT striker is a great achievement. So far only 9 players scorred so many goals in Europe (Dzeko is close) and that doesn't take away anything from the players you mentioned, but is a proof of Lukaku's quality.
It's a nice feat but gets overrated since this is a modern thing. Prior to the mid 90s it was near impossible to get over 50 NT goals because Europeans rarely played more than 80 games and those who did reach those numbers played against tougher/more level competition. There wasn't any Andorra, Gibraltar, San Marino, Liechtenstein, Kazakhstan, Estonia, Lithuania, Malta etc and you had an entire Yugoslavia and entire USSR instead of Croatia, Russia, Serbia, Ukraine and a bunch of others that don't really pose much of a threat like Montenegro, Belarus etc.
The Americas are pretty much the same, Asia is rather similar as well, so is Africa. Europe has seen the most change, to the extent of adding more games, more low value games, which causes more goals to be scored by top teams. Asians always had the most inflated numbers and in the last 15-20 years the European players will resemble those with 150 caps and 100 goals etc.
If you look at the top scorers of Europe before the 1990s, we have Puskas and Kocsis. 84 goals in 85 caps for Puskas and Kocsis had 75 goals in 68 caps! Gerd Muller had 68 goals in 62 caps!
https://en.wikipedia.org/wiki/List_of_men's_footballers_with_50_or_more_international_goals
You can see that the majority of European players on this list is more modern as they started their career in the late 90s and on. Only a handful are older and you can see how many games less they played!
Italy doesn't even have players with over 40 goals and all three players with 30+ played before the 70s! The modern ones are also not benefitting from caps, as other than Del Piero, not many forwards had over 60 caps! (Totti 58, Inzaghi 57, Vieri 49, Baggio 56, Toni 47, Immobile 46, Di Natale 42, Casiraghi 44, Balotelli 36). Lukaku has 93 caps, 22 of his goals are in friendlies (37% of total) while 13 other goals came against NTs that didn't exist before the 90s! Nine came from the Nations League, but let's call that a proper tournament for the sake of argument. 0The comparison of European international goals just shouldn't be done in this way. The competition is completely different now. Great feat and all that, but don't make it sound near impossible. It's just another sign of our times.
The older guys also played a bunch of friendlies because there wasn't much else. I think they ought to be removed from these lists. Don't see why they still count.