However, research in the area of expert performance shows that when it comes to this practice, not just the amount, but the type of practice matters tremendously. How practice is done is such a major factor in improvement that taking the 10,000 hour rule by itself is like solving physics problems with the formula F = a instead of F = ma.
Research in the area shows that performers usually plateau after reaching competence, which is the point they no longer struggle with regular operations. At this point, automaticity takes over, which for example is the reason that whilst most people can walk, few get consistently better at it despite walking a lot. This means, that out of the 10,000 hours put into learning the task, 9,000 are potentially wasted.
In order to leave plateaus, one needs engage in "deliberate practice", a term coined by the cognitive psychologist Anders Ericsson. It's presence, or lack thereof has been shown across a wide variety of disciplines between masters and people who are merely good after having spent similar amounts of time on practice.
Deliberate practice is practice where you consciously strain for a point that is just outside your current skill level. In the case of musicians for example, it can manifest as slowing down a song to a crawl until every note is hit in the right way, and then slowly speeding up or slowing down again at the line where one starts making mistakes.
My point is that whilst the 10,000 hour rule is useful for setting time expectations to become a master at a task and helps illustrate how expertise is attainable for all of us if we put in the time and work, it lacks predictive power for whether you will become great at something after spending this amount of time.
For a hobby, this may only result in some wasted practice time getting to competence(I've eyeballed this at about a factor of 2 doing some testing learning the piano, unscientific, I know), which is perfectly fine. You're doing it for fun. Pain periods and all.
For an occupation, however, it can lead to endless grief. You've read about the 10,000 hour rule, you want to become very good, but after a year of work, you don't ever become significantly better. You sit there, grasping at the problem, but it's elusive, like you're wildly tweaking screen settings things to fix a kernel bug.
I am also oversimplifying a bit for brevity here, but there's some books on the topic. For an in depth review, there's the "Cambridge Handbook of Expertise and Expert Performance".
For a lighter book more along the lines of Outliers, theres "The Talent Code" by Daniel Coyle. AFAIK, both draw from the Cambridge book.
Both of them are worth a look, the 10,000 hour rule might tell you "I can do it", but these will tell you "How to do it".
If you can get a skilled spotter, or a coach who knows his/her stuff, nothing like it! I have to rely on myself unfortunately, and am very grateful for the super materials that I've found for learning the guitar. Like you, I am focusing on the fundamentals and patiently letting my skills build up. 2 years into it I am happy to say that it's looking good!