Now, a team working on a set of core books is a different story. When the pieces are broken up into manageable units, you really do care. I care about the rogue and the warlock because I had a hand in making them (and I'm playing them to make sure nobody screws them up

). Rob Heinsoo and Mike Mearls really care about the fighter because they had a major role in deciding how it worked.
Everybody working on the book is passionate about something, whether it's the halfling, or the cleric, or feats, or the Athletics skill, or magic items, or DM advice. (You wouldn't believe the debate we had about whether attacking around a corner should take a cover penalty!) The team approach to these books makes sure every nook and cranny of the rules gets the scrutiny it should.