Writing a song is simply a matter of arranging thoughts, phrases and words in a particular order so , yes, anybody can write a song, but whether that song resonates with other people depends on things like charisma, insight, intelligence, delivery, attitude, inclusivity, empathy, musical knowledge, language skills etc.
A songwriter arranges words, phrases, sentences and ideas into a form which carries a message. The message is reinforced with music and will be fixed or set in a particular way which is repeatable and which can be learned, understood and redistributed among other people.
The music and words of the song will usually fit an expected pattern or genre. Genres can be geographically specific, local, global or simply fit some kind of musical expectation.
In western music, a songwriter may only write the words and a basic chord structure; then a producer will create extra harmonies and instrumentation. Although, it is also common for the songwriter to add these, depending on their ability and personal taste.
Songwriters create art out of conflict, difficulty, joy or any other aspect of humanity worthy of comment. They may write popular or unpopular songs. Throughout history, songwriters have an important role to record events as they actually are and to gauge public opinion; both capturing it and expressing it in a way which is easy to remember and reminds people of emotions felt at the time.
If they wish to become professional, they also need to be extremely tough willed, good people managers and be able to suspend their sensitive instincts. A touch of charisma may also be required.
In my experience, these labels are complete nonsense. Skill, gift or talent all come from being highly motivated.
In fact, it's deeply insulting when people say a musician is gifted because it implies the skill they have was given to them. It was not. They spent years, even decades learning the nuances of their craft. It was hard work and they will have had lots of times when they got stuck wanted to give up.
Songwriting is a skill you acquire through dedication. You develop a talent for it after years of getting it wrong and making lots of mistakes. It is not given to anyone.
Mostly made. There are some who believe that having musician parents helps us develop musical skills far earlier. But that doesn't help much with all the other skills, mentioned above, which a songwriter needs.
Exposure to other songwriters and an emotional personality are largely a product of environment and nurture.
Yes, songwriting can be learned. Nobody was born with a pen in their hand and every one has to learn empathy, sensitivity and everything else. It's just a question of being motivated.
Absolutely not.
Being able to read music will help you be a better musician and musicians usually write better songs quicker than none musicians, but not always.
Songwriters need to play a polyphonic instrument such as piano, guitar or ukulele. They also need a basic grounding in music theory, but being able to read music is not important.
It is far more important to have good language skills, be empathic and have an inquiring mind, especially of humanity with all it's contradictions.
Some are, some are not. This depends very much on the audience, genre and subject of the songs.
Jazz and classical songs require a different approach to rap or hip-hop. And within each genre there will be a 'depth' to the message depending on the subject of the song and ability of the writer.
The deeper the message, the more layers, and more layers will require more intelligent writing to hold it all together whilst illustrating the individual strands.
It's fair to say, a songwriter needs to be intelligent enough to be in touch with their audience, their genre and subject of their songs. They need to apply themselves to the message, but that need not be mind-blowingly complex. It just needs to touch people emotionally.
So, intelligence is not a pre-requisite for being a good songwriter, but can help make better songs.