Is there something about 3e that diminishes the importance of role-playing?
Not in the three core rulebooks. I like many things in RPGs, and role-playing immersion is just one of them. Strategy is another. Painting minis and building cool set-ups is another. Writing backgrounds, coming up with cool ideas, and enjoying the food people bring at the game session are yet other things I like about it. I truly think you can have strategy and role-playing in a single session. They are not exclusive towards one another.
The opinion they oppose each other by essence comes from the sources of RPGs, when suddenly guys concidered the minis on the table with the first person and thought "hey, this isn't a wargame anymore, that's a ... a... role-playing game!"
RPGs have evolved from there to find an identity of their own. Some started to promote character immersion and ambiance, to point the finger at "powergamers" and "leveling-up". To concider RPGs as something of an art. Call of Cthulhu became the Holy Grail of these people at one time (and let's face it, it's still a kick-ass game, so I don't mean to bash it). (Much) later came a myriad of immersive RPGs, among which the World of Darkness series definitely was a corner stone.
Meanwhile, some people went down another path. RPG systems had to be as precise as they could be. Believability went through a system that represented reality with the most accuracy, first. These people went through RoleMaster and rules-heavy games.
In many ways, D&D3 is like a cousin, or a bastard son, of RoleMaster. Like a RM lite, without critical tables and rolls without limit, a d20 instead of d100, but still fairly comparable to RM (stats generating bonuses applied to skills, skill points per character levels, myriad of character classes and so on). Add to this the design concept of pleasing the D&D fans out there who loved miniatures, and you have the implementation of a movement and combat tactics & strategy into the game.
The guys of the "immersion" school see that as a shame and a great step backwards for the "art of role-playing".
I think they're wrong. Wrong because one "school" is not superior to another. There is no universally best way to enjoy RPGs. If there is such as thing as a "right way", this is whichever way pleases most the people around the game table and of course, it varies greatly from table to table. The rest is egotistic diatribs.
I think D&D went back to its roots while incorporating some of the experience gained with other RPG experiments (like an integrated skills system, for one). I think it's good, because D&D didn't forget its identity and what makes it fun (fun as in "game" ) for so many people.