Mainly because they dictated play a lot more and better than he did.
I don't agree with that assessment.
Modric is not a controller. Pirlo, yes. Kroos acted more like the controller in real Madrid. Paul Scholes has played as a second striker, a regular central midfielder and a controller.
What version of Paul Scholes are you comparing to Modric?
In terms of controlling games and passing, Scholes is superior to Modric. In terms of defending (especially in a low block) and press resistance, Modric is superior. Goal scoring, we saw that Scholes could play as a second striker and scored a lot more goals than Modric ever did or could.
Modric is more of an all round midfielder that was competent in a lot of areas, but his main asset is his extreme press resistance that arguably be matched by only Xavi Hernandez.
What also has to be taken into consideration is the teams they played for and the 'perception'. In fact, the English media did not rate Pirlo till he dominated them in the 2012 Europs similar to how Zlatan Ibrahimovic wasn't really that rated till he scored that amazing Bicycle kick against them.
Had Modric played for Manchester United, would he have done any better? I doubt it.
Modric's game did not change that much from his Tottenham days, the only difference is he played for Real Madrid and performed at a Higher level (Which he contributed to of course).
I think Modric is "greater" than Scholes because of his achievements and his "big game" performances, but in terms of their skill sets at various times, I would argue Scholes was superior.
In terms of greatness, I would say:
Modric
Pirlo
Scholes