I wasn't really referring to exploration or resource management - I have yet to experience them in play. My objection is towards sticking with the old D&D races, classes and alignments, and things like restricting which race can be which class.
Ah, I gotcha. Well, I think if you look through the alignments on page (I want to say 30 or 31?), you'll find very robust ethos statements. You don't have to start with the alignments provided as defaults for each class. You can certainly use those. I'm a huge fan of the alignment system in DW as it, and Bonds, actually drives play both mechanically and from a thematic conflict perspective. The simple, overt, and transparent cues provide the GM with precise information on what sorts of conflicts to frame the PCs into (in the same way 4e's Quest system and Themes/PPs/EDs do). Simultaneously, like any good feedback should do, their clarity, focus, and mild constraints incentivize players to play to archetype.
You should feel free to open up the game as you see fit. Latorra expressly speaks to it later in the book. What's more, the system's resolution mechanics are so elegant that the system is robust to changes or homemade material. Creating a Dwarven or Tiefling Druid is as simple as coming up with a singular, theme-driven racial mechanic that marries the race and the class together with the resolution mechanics. For instance:
Druid
Dwarf
Stoneblood is a mundane term of endearment amongst your people. For you, its an actual blessing from the primal spirits. In addition to any other attunements, the Towering Mountains is always considered your land.
Tiefling
Hellfire is your spirit's home and your heart is a furnace because of it. When you
take damage while shapeshifted you may choose to revert to your natural form to deal 1d4 environmental damage to your enemy from fire.
Finally, with the multiclassing inherent to several classes, you can make all kinds of combos off the basic chassis available. However, if that isn't enough, there are lots of great compendium classes out there (from Warlock to Fighter/Mage Duelist etc). If you're planning on running something for your players and they're looking for PC build material that isn't drawn up explicitly in the book, just post it here or PM me. I can easily whip something up for you guys that is fun, balanced, and plays to archetype/theme.