Symmetry is not beautiful by itself but only when it is conditioned upon evolutionary factors such as survival, procreation, and the likes.
In addition some features are conditioned and relative to either male or female. What is beauty [aesthetic] to the male may not be beauty to the female and vice-versa.
Males find the higher hips to shoulder ratio more beautiful and sexy while the female will favor a higher shoulder to hips ratio. The hips to shoulder ratio in general has evolutionary advantage to mankind in terms of procreation and other advantages. A female with very small hips, thus smaller hips to shoulder ratio will likely to face birth difficulty in general.
Symmetry in the physical bodies of the male or female denote general [not specific] health of the person and thus has first impression significance. The physiological elements are controlled by two separate hemispheres in the brain. Any defects in one side [sign of non-symmetry] and thus an imbalance function in the brain. Wherever there is a significant difference between the two sides of the physical body, then there is a likely possible of something is wrong and the person is not as healthy as the average person.
Thus asymmetry is a sign and warning for the opposite sex or others to be careful and investigate further in making decisions that are relevant to the matter.
The above issues are instinctual and most people in the modern era do not bother about instincts and intuitions any way.
Any one into photography or art?
Re the aesthetic elements of photography or art [general, not modern], what is beauty in this fields are driven by evolutionary and survival elements.
The Rule of Thirds
digital-photography-school.com/rule-of-thirds/
In photography as in art [general] one must follow the Rule of Thirds generally to ensure one’s photograph is considered to have aesthetic [beauty] value.
This is directly linked to evolutionary elements of survival and the position of they eyes to hunt from food and dealing with enemies, etc.
By obeying the Rule of the Thirds, the main subject[s] are placed in alignment with the position of the two eyes and thus there is no stress and extra effort of the eyes to move from its normal position.
Subject in the Middle - A Taboo
In contrast, in general [there are exceptions, portraits, etc.] it is a serious Taboo to put the main subject in the middle. This is because the main subject in the middle forced the two eyes to focus into the center and away from its normal position and thus make one very uncomfortable if the focus need to be kept for a long time.
Level Horizon
If the horizon in a photograph is not level, then the photo is marked down in terms of aesthetic.
A level horizon is pertinent to facilitate hunting in the savannah or plains to assess the position of the prey [food]. An unlevel horizon in a photo can give many a headache as the brain has to use efforts to right it.
Note there are exceptions to the above, but they are besides the point.
So, what is beauty to humans is conditioned upon survival, procreation, and the continuation of the next generation of humans.
There is no intrinsic beauty by itself.