Someone with a black belt hasn't mastered their art. Certainly not if they're only a first dan! With martial arts, there is always room for improvement, just as there is in anything.
When can you say you're in great shape? When you look at yourself, know what your body can do, and you say "Hey, I'm in great shape!" Okay, so you can do burpees and clapping push-ups - can you do a pull-up? How good is your balance? Would you be able to carry someone if you needed to? Perhaps you might try looking at functional fitness. In the real world, it's unlikely that you're going to have to do burpees (and I, for one, am happy about that! ), but you might have to run away from a dangerous situation. How good are you at getting over a fence? You can run a 6-minute mile - is that over rough terrain? What about your rotational strength that helps, throw a punch, do a good round kick, or just heave over a suitcase. How is your grip strength?
There are so many other things you can look at. What I like to do is watch action shows and see what sorts of moves are useful in those sorts of situations. Not many push-ups get done, but lots of punches, scrambling over chain fences, slashing with swords, etc.
Fitness, also, is not just a physical thing. The brain must also be kept fit, not only through doing different physical activities but also mental ones. Try some meditation to improve focus or creativity or whatever. Learn a language or craft. Check this out for example.
Great shape and Mastery are really two different things. I suppose it all depends on what your goal actually is.

I think that's subjective. As TopNotch mentioned, just because someone is a black belt doesn't mean they mastered their art. There are 10 Dans in Karate, and those who just reach the 10th are pretty much on their 80s, and yet, limiting yourself to just one style isn't enough.

In my opinion, this is something that, as all things goes with fitness, is personal to yourself: the limits of your body, your needs, your goals... To some, learning complex calisthenic moves, like Flags, is enough. To others is for how long they can keep a Flag.

Running long distances, exerting the same amount of strength over long periods of time... Resistance is something that is good in survival situations, and Burpees are a good way build up resistance.

From my point of view, fitness is just a tool, or a range of tools that allow you to do the things that you really want to do in life. Fitness has meant different things to me throughout my life, whether that was as a teenager playing basketball or as a soldier in my 20s. So too would fitness mean something different from someone in their 70s, who would probably regard fitness simply as the means by which they can stay active and mobile and delay the decline of their functions. The idea of mastery over fitness is therefore a bit misleading. Would you say that you mastered painting if you were really good at brush strokes but had never painted anything? By that I mean to say, that it is possible to master a tool, but you need to do something with it to be a true master. To go back to the example of martial arts, would you consider a true master to be someone who practiced alone in their dojo since 20 years, or someone who has won tournaments or other fights? The 6 minute mile is a pretty good standard, that is supposedly what Navy Seals have to run under in order to pass selection training. They also have to run that time in combat boots on sand though.

My long term "fitness" goals are more like actual accomplishments. I want to kayak the length of an entire river. I want to run a marathon in some place interesting. I want to complete a triathlon at my family's cottage. Things like that. I am not sure if I will ever get around to doing them, but I would only consider myself a master when I took what I had practiced and applied it in a real world setting.

I think too that people when they look to say that they are elite in terms of fitness forget the third element of fitness, which is agility. The accomplishments that you listed represent strength and endurance. Can you do advanced yoga moves? Can you balance on a bosu ball while people try to knock you off? There is probably a lot to fitness which you are overlooking, as do we all.

Master of the Universe

Something else you might try:

I'm still working on pistol squats, when mastered then dragon squat.

I agree with everyone regarding using the term "mastered fitness". I don't think that's possible. I DO believe there comes a point in my journey where I understand what works for me to get the results that I want. But I believe there are SO many choices regarding fitness and it means different things to each person. So, I don't think it's possible to know and be able to perform every type of fitness.

Fitness is a journey. Not a destination.