Warning: long read.
I'm not sure if the bold part is a joke or not, but I'll assume it's not, so I can say... that I strongly disagree with it. More specifically, I strongly disagree with the underlined word. I mean, how can something that is so intrinsically attached to the inner self of a person be considered somewhat close to objective?
Objectivity is not something as common as people may think: something purely and trully objective is something that cannot be denied by any means except by questioning the methods used to measure it (or just plainly lying). In this case, I have to ask: which attributes are being analized, measured and compared so that one can reach the unarguable and undeniable conclusion that a certain personality is better than the others? And what is/are the method(s) used to measure those attributes and compare them to each other?
In my opinion, the "quality" of any given personality should only be measured on a one-by-one basis, taking into account the context of the person and their feelings regarding the way they are. If you feel so good about yourself that you think your personality is the best, then there's no doubt that your personality is the best... for you in your specific case and situation - that is, subjectively speaking. However, another person who'd have an ESFP personality could also feel the same way about themselves, so ESFP would be the best personality for them in their specific case and situation, and the one that fits them the best. So then, how can we say that one of both is the best personality objectively speaking?
Also, you have to take something else into account: so far, we're only talking about the abstraction of personalities, that is, a stereotyped and oversimplified reduction of reality. But if we think about the different manifestations of a certain personality in real life, the task of measuring and deciding which one is the best becomes (almost) impossible. And that's not only because different people with the same base personality have (slightly) different traits from one another, but also because personalities themselves are not immutable: they evolve with every passing year, which means that (almost) no one has the same personality in their teens than in their sixties. So even if the core part of a certain person remains the same and their type of personality keeps unchanged, there will always be a lot of little variations over time that could generate big differences in the way they think or behave, or in their attitude towards life.
So, having all that in mind, the question is: which one of that myriad of slightly different variations of a certain type of personality would be considered the best and how would that be decided? And a very reasonable answer would be that doing so is just such a titanic task that is not even worth thinking about trying it.
And that's exactly why we need to unify them in a little bunch of general and more abstract types. But, in order to do that, we cannot just go ask literally everyone in the world, because that would be impossible; instead, we use statistics, that is, we take a very little sample of people and extrapolate the results to the whole humanity, leaving aside not only the little individual traits that can end up making huge differences, but also all the nuances derived from the distinct societies and cultures that can also make huge differences. So, in the end, even if the results of the tests are more or less accurate (like in this case are), they will never be fully representative of reality, due to their way too limited scope.
And that's not all. If we read the FAQ section of the website that hosts this test, we can see at least three variables that speak too little about unarguable and undeniable facts: first, the same personalities may differ from one website to another, due to the diversity of theories and approaches used; second, the results of the tests may vary even under this same website if we make them in different moments in time, because they are "countinuously refining the test questions"; and third, our own answers may be subject to our mood, thoughts, wishes or any other subjective stuff that we can factor in when answering the test.
So to sum it up:
1) a personality can only be considered better or worse in relation to the person who has it and their circumstances (including social context, culture and other more personal stuff), which are always changing;
2) the results of the test depend heavily on purely subjective answers from the person doing it;
3) the test itself may vary when done in different times, due to ongoing changes and improvements;
4) the methods and approaches used to describe these same types of personalities may differ from one website to another; and
5) on its core, this is all based on statistics, which are an inexact and reductive discipline.
In other words, there's literally nothing that comes even close to objectivity here: everything can be argued and called into question. Even if the results of the tests were 100% realiable and they were the same all of the time across all of the websites irrespective of all the methods and approaches used, we'd still have to overcome the huge problem of how we could analyze and measure that data so that we reached the undeniable conclusion that a personality is the best in absolute terms, regardless of the context of a given person and how they feel about it. How's that even possible?
Besides, something I've noticed with the word 'objective' and its derivatives is that people generally use them when they want to be right (whether they actually are or not), so, in a way, the mere use of the word 'objective' is usually very subjective. Although, of course, this doesn't apply always or to everyone and it may not apply to you here, because that's nothing but a subjective observation. In fact, it wasn't that what drew my attention to your post, but the context in which the word 'objective' is used here, refering to something that by its very nature is like an almost perfect antithesis of something objective. It puzzled me a bit when I read it the first time.
Anyways, I think it's time to finish this unnecessary speech, but I want to do it with a little reflection related to time.
Time can be precisely measured, to the extent that we can even be aware of the exact second we're living in. And, in this day and age, when all our devices are perfectly synchronized and automatically updated to adjust to the world time, we literally have in our hands the most accurate time possible at any given moment. So we can say without a glimpse of doubt that time, when converted into the same time zone, is a totally objective value, right? I mean, who would even dare to say that time is subjective? It is clearly not, and anyone with a smartphone in their pockets can prove it right away.
And that's indeed true... until we add relativity into the equation. When we do that, relativity just cracks open the door and slaps in our faces with not one, but two interesting facts about time: first, the more someone moves away from the surface of the Earth, the slower time goes by for that person; and second, the faster someone moves in general, the slower time goes by for them. Thus, if someone was crazy enough to say that something as easily measurable and commonly considered objective as time isn't totally objective or even go as far as to state that it's purely subjective, that person could still have a point and duly justify it without any kind of mental gymnastics, just using physics (and they wouldn't be wrong; maybe not necessarily right, but not wrong either).
Of course, the differences resulting of these peculiarities of time are negligible to common people like us (they'd be measured in nanoseconds, picoseconds or even less) and, even if they were somewhat noticeable, our automatically updated devices wouldn't let us know it, because they would update to the world time as soon as they could connect to the internet. But the point is that those differences are still there: we're not aware of them and don't have reasons to care, but they exist, allowing a guy like me talk about how relative (pun intended) objectivity is.
But, needless to say, all I wrote here is far from being an objective truth, so it can be argued and refuted, and I can easily be proven wrong.