Maybe that's how you'd do it. But we enjoy making games, it's not work to us. It's not a factory assembly line where we just want to add more and more people to get the game done faster.
Hiring people to do it for us isn't what we started making games for.
I had always assumed that with hiring for this kind of job, you reach a point of diminishing returns -- there's only so many people you can throw at a particular task anyway. I also had the idea that too many cooks in the kitchen make a bad soup, and FP didn't want to water down their vision with too many potentially conflicting ideas.
Edited:
If it were a rewrite, I'd be whining. It was a re-design and re-architecting and re-platforming. If they had just rewrote Legacy with better designed code, I'd have to think it'd be done by now.
They took the long way round, and will hopefully get back to legacy after picking up a whole bunch of game improving hitchhiking features along the way.
If you were totally happy with legacy, go play it. I personally want to see more out of the game -- as much as I love legacy, FP can improve on that formula.