I definitely agree that measuring from the wrist to the floor (static) can work really well and will probably give an accurate fitting much of the time. For the average player, yes, it can probably be sufficient. However, I do believe posture at address is very important as well. And how a person swings the club (dynamic) definitely plays another important role in fitting the length and lie of clubs. IMO, though, it is absolutely necessary to hit the clubs at different lengths to see how they actually perform in action.
If you had to choose just one, measuring from the wrists would be the one choose, but if you can do the others as well, you'll get the most accurate fit.