And how is "his presence" supposed to do this? Even if he drags the concentration of defenders to him, you can't be serious if you compare this completely mental effect to Modric's direct impact on the game. He has been Madrid's engine alongside Kroos for the past 4-5 years and clearly makes it so much easier for every of his team mates by dominating the midfield, distributing the ball and initiating chances/attacks.
I mean, it is not like Ronaldo constantly has two or three markers on him following him everywhere on the pitch which would create space for his comrades. Cristiano isn't particularly dangerous outside the box anymore so why should teams care about marking him in these areas? In terms of creating momentum out of static situations, there are at least five or six players in Madrid's side who are better than him.