You mix up knowledge, skills and proficiencies.
If you watch 10 youtube videos, you might gain the knowledge of building a kitchen, but you neither gained the skills of using tools, nor the proficiency of planning and building a kitchen.
Those are very distinct things, which pedagogues are aware of.
It has to do with experience because skills can only be honed through experience. It has to do with age because honing skills via experience requires time.
Yes, but it does not take a learner lots of experience to learn a skill (with some caveats, ofc). It takes the teacher experience to teach a skill, though.
> It has to do with age because honing skills via experience requires time.
I agree.
But it was not about honing skills or becoming perfect, it was about learning and "building a kitchen".
We must have different priors regarding OP's specific example. I think that "building a kitchen" would require a hell of a lot of skill, all of which needs to be honed over a decent period of time. I'm 100% confident that given an empty room, building materials, tools, and some appliances, I would do more harm than good.
I'm not saying experience is irrelevant, I'm saying you can teach somebody the skills to use tools and the proficiency to build a kitchen and he would afterwards be able to build a kitchen, even though his experience is very little.
I'm not saying it will be the best kitchen in the world, neither am I saying the teaching process will be super fast (it depends on teacher and pupil), but I am saying that it is first and foremost not about the age and experience of the trainee, who then later attempts to build the kitchen.
The time investment is necessary. It is by no means sufficient.