My question here is this.
Who decides whether a person has the "psychological ability to willingly and under awareness agree to be with someone while being informed of what such things would imply and its consequences".
On what basis is it decided commonly?
Isn't it all based on Age, and not the actual mentally of the person in question.
There's a thing called mental development stages
https://en.wikipedia.org/wiki/Cognitive_development
While not everyone develops at the same rate, there's an assumed rate of normalcy in how an organism psychological capabilities should develop if they are properly nurtured, so yes age is a strong indicator of mental maturity, but how that brain is helped to develop is also important
We humans are not some massproduced product. Aka., each and every person is different both physically & mentally since the moment we are born.
So, making something a standard for everyone based on some random age criteria isn't really a appropriate.
It is not random nor arbitrary, a person around 16 years old under normal circumstances (what are "normal" circumstances you ask? it has access to physical and psychological safety, this means, it is not nutritionally neglected, physically or mentally abused, it is not under the effects of grave illnesses, neglect, has access to a base social support circle, and an enverioment that allows it to explore, learn, and develop ideas freely) should be psychologically mature enough to handle conversations around sex, while not necessarily ready to engage with sex even if their bodies can procreate, otherwise this development will take longer to take place, or never develop
However 16 is a common bare minimum age number, this development doesn't comes earlier than 16
In fact the brain doesn't stops fully maturing until around age 23, and even then a person is considered just a young adult
I mean, worldwide 16 years and older is considered as average for sexual interaction around the world by law, but some still question and say that it's not right age just because their country has different tandard for it. Some countries even have it as high as 25 years of age or not legally allow it unless married. Isn't it all based on some random assumption rather than individual qualities.
The age of consent with parental permission is set as low as 16 because it means to allocate case in which teenagers have sex with each other, or because those countries didn't had an age of consent or laws againts sex with minors at all, like it is the case for Japan who didn't had any laws regarding sex with minors and the production, distribution, comersalization, and ownership of media depicting sex with minors unit late 1990, and in fact ownership of CP didn't became illegal in Japan until 2014
Those changes were imposed by foreign pressure, so in order to not criminalize a huge part of the population who had married young, or engaged in sex with youngsters, the age of consent was set around 13, and then periodically raised to 16-18, this was based on practicality and not on what is just or fair towards children
What I am saying is that all these stuff isn't dependent on age, because everything including psychological state of mind is a unique trait for ever individual.
I don't expect you to spend time reading an entire Wiki article on psychological theory, but, i would recommend you to at least, minimum read the Erik Erikson's theory of Cognitive Development
As to why cognitive development is linked to Age, well that's a longer read and you can do it, whenever you feel like it and start here
https://en.wikipedia.org/wiki/Child_development#Mental_and_emotional_aspects_of_development
Some mature mentally as early as their early teens or even pre-adolescent and others take years or never mentally mature until they die (not talking about mentally disabled people here). And this isn't just talk about sexual decision making, it's about everything. Not ever aspect has to be taken as sexual.
That's just plain false, no human reach mental maturity as a per-adolescent, it is by definition a contradiction, it is like saying that an toddler can talk, just like that comment ignores the development stages of vocal chords, you are ignoring the development stages of both the brain and the endocrine system
And listen i am not denying that there's immature, irresponsible, and plain dumb adults out there, but what i need you to understand, is that the brain which is a part of the human body requires a minimum amount of years and experiences in this world before it can even properly deal with certain things, from walking, to talking, to understanding the concept of permanence, of ownership, of otherness, etc. and that includes understanding the concept of sex let alone actually engaging in and experiencing sex