Had an interesting, open ended question recently posed to me.
"how long does it take to aquire a level of skill to be considered a good WW?"
This persons asperations are to be able to handle any moderate to difficult plans. Produce a quality product. And be able to "just visualize something and just go ahead and make it" as I do. I'm not patting myself on the back here folks. I just had a friend ask me to help him "make" something and I just did it, a bookcase to fit a space, to his amazement. Now this led to a 1/2 hrs discussion as we banged out his project.
This guy has a good mechanical aptitude coupled with decent manual dexterity. I told him with a good basic shop at his disposal it wouldn't take him long to be going strong. He's quick to pick up on what I'm doing when he's hanging around. The next logical question of course was "well how long is not to long" my response was "it's inversely proportional to his desire".
Good answer? So how long does it take to make a "good" woodworker?
As long as it takes, no more and no less. There cannot be a single answer because it depends at least upon a person's aptitude, desire, previous experience, and availability of time to spend in the shop. What is meant by good? I can think of plenty of examples of good things, but could not define the word (at least not without a very specific context). The qualities that make a picture frame good to me do not all apply to a table or box.
Either you have it or you don't. Some people will always have to have a plan. Other like you and myself are just as comfortable without them. I think that it is an ability that God blessed some people with. I think that is comparable to a musical talent or a sports talent.
It's takes a lifetime. You never stop learning. No project is exactly like any other.
Learning rate is also dependent on how many projects you do. If you only make one project a year it'll take you much more calendar time to log the same # of hours of shop time that a man making a project per week will get.
Used to be that kids would start apprenticing at 12 or so and be journeymen by 18 and master by 30. This is full time - you do the math.
Today with power tools a lot of the old skills are easier to learn or not needed as often. But long term craftsmanship takes time, not just calendar time, but shop time.
OK I jump in. It all depends. All of the above answers are right. But, it also depends a lot on the individual. You used the term "good mechanical aptitude coupled with decent manual dexterity", and that is important, but not sufficient. I think that some people are born to create and others are not. It is not a judgement, it is just an observation. There are a few of us that can go into the shop and build something functional that looks nice and will stay together for a life time and that is great. There are a handful of people that do the same thing and end up with works of Art that end up in the smithsonian. Why I can't say, but I understand the difference. I am an engineer that took 6 art history classes in College. I love art, dance, theater. I spend lots of time with people that have a gift that I don't. I am a good wood worker, My pieces last and look nice. They are not art.
You friend could be one of the creators. It could take him a few years to develop the skills to make wood stay together. It could take forever. Passion is one of the things that makes a wood worker. To see the end before you start, to put some of your soul into the wood, to give more live to a living thing.
Can someone learn to follow plans and build a table or a bookcase? yes! Can they learn the passion? No!