If you're looking for a big system that can stand up to long-term campaign play as well as D&D but is designed with contemporary design sensibilities, BWG is the game for you.
The Burning Wheel system has introduced a host of design innovations over the years. A few examples: with the fail forward mentality a missed die roll isn't a failure, it's an unexpected outcome; instead of the GM designing adventures, players direct the action by listing their beliefs and what they intend to do about them; players can make world-setting contributions by creating NPCs using the Circles mechanic or historical facts using the Wises mechanic; and players develop rich character concepts using an elaborate (and fun) Lifepaths mechanic reminiscent of Traveller.I don't think I could sum up what's wrong with "contemporary design sensibilities" any better than the above list. Of course "contemporary design sensibilities" is code for "better" in whatever field it appears in, often about 5 years before those sensibilities are thrown out and regarded as brain-dead crap by the next wave.
Design sensibilities are subjective and "contemporary" or "modern" or "avant garde" are just stamps people stick on them to make them sound objective. By dint of being subjective, of course, there are always people who don't agree with them - often quite contemporary people.