You don't draft players solely on the premise of what they will do in 5 years time, you also consider what their current output will be like the year after. Say for example (just using Watts and Rich don't mean any of it) that Rich plays at a very good/elite level after a year in the system and does this for 11 years, but Watts has 5 years to get to Rich's current level and then passes him but not by much and has 7 years of elite footy which would you prefer. It is a hard choice and one must consider where your team currently is and if they want a premiership now etc. I will just reiterate that this as just a factless/baseless example completely off topic.
Obviously we considered Watts the elite talent of the draft and at the same time a gun key forward isn't easy to find, just ask the Bulldogs and a host of other clubs. Melb pretty much had to build their forward line and midfield, so plenty of consideration would have been given to Rich. We rated Rich top 3. Ultimately we had to choose one. Our clubs were/are at different stages of development.
We're building from the ground up a team capable of winning a flag in 5-7 years. Watts' output in 5 years was always going to be more important than what he'd do in 1-3.