It's just down to the ninety-ninety rule... The first 90 percent of the code accounts for the first 90 percent of the development time. The remaining 10 percent of the code accounts for the other 90 percent of the development time :) That last stretch takes so much more effort than people realise. Keep it up, you're doing great.
True that! I worked on a few AAA titles and with a such experience I wanted to have a different approach. And while I avoided lots of pitfalls, I did other mistakes but that division of development time still holds up. Is just spread a little bit differently. One day I want to write a post mortem to the game and will cover all of that :)
And thanks!