I hesitate to ask what you're defining as "modern". Between Arcana Evolved and the Book of Experimental Might, I'd say Monte's name is on some of the most significant (and significantly advanced) d20 books released after 3e. I think they hired him because he understands the 3.X architecture and may have some ideas on how to improve it. Although I admittedly haven't read FantasyCraft or some of the other 3.X derivatives, I don't think I've ever seen a more "modern" rpg than 3.5 D&D.
I would loosely define "modern" as a game with a unified ruleset, equal emphasis on combat and noncombat activity, a strongly reality-based design, and highly modular design (the "toolkit" mentality). I would define "classic" as being focused on the Chainmail-esque tactical miniatures combat in a dungeon setting, using many discrete subsystems and esoteric rules, and without making many explicit attempts within the rules to model reality or to encourage activities other than combat. By these definitions (the ones that I just made up which no one else is bound to), the announced 5e plans (and Monte Cook's work) are pretty modern.
Just goes to show how exposure to different games changes what you think of as modern. 3.5 isn't really modern at all, compare it to BRP or ShadowRun 2nd Ed, and there isn't anything really new about it at all. D20 itself was just catching up to what other systems had been doing in the 80s.
I'd also suggest that the unified mechanic drives things towards combat more than less, particularly when you have rules for combat and rules for everything else. When mechanically bluffing someone is the same as crafting a breastplate (and is just a single roll of a die, with minimal modification or interaction with other rolls, something skill challenges tried to address but didn't do well enough), there isn't all that much interest in doing any of it, because it's all the same.
Contrast that with BECMI/RC D&D, which as you advanced had rules for settling down and running a kingdom and even becoming a god. Tons of stuff that really isn't combat at all, and there was the convention of just figuring out how to resolve an action or conflict that didn't have specific rules instead of feeling stonewalled by the lack of support in the rulebook (an attitude that has become rather more prevalent since d20). You can be certain that playing an RC game over a period of time will leave you with a much more diverse play experience than playing 3.5 would.
The result of the unified mechanic in a classical system (which 3.5 definitely is, and 4e still fits in a lot of ways) results in more of a combat focus, not less of one. 4e at least forces everyone out of combat a bit with skill challenges, but in a clunky way, 3e and 3.5 didn't even offer that.
If you want to see a real modern system, look at one of the FATE based systems. I suggest Legend of Anglerre if you're interested in sticking to fantasy, Diaspora if you want to look at some interesting hard-ish sci-fi. ORE systems also really open things up, and are far more modern, with Monsters and Other Childish Things and A Dirty World being excellent examples of taking the focus away from combat (while not stripping combat out entirely). They both do use a unified mechanic, but BRP did that 30 years ago, so while 3.5 does share that characteristic with the FATE and ORE games, it has existed for so long that I wouldn't accept it as one for a modern game any more than use of dice makes a game modern.