I am working as an SEO for the last three years and everything which I specifically do for Search Engine keeps on changing. It never remains static. Secondly, what is good for one website is not good for another website even in the same niche.

That's what makes me believe that SEO is neither an art and science, it's just hit and trial method of achieving things.

There is only one thing which I believe that remains static is the "creation of quality content for the user"

Please answer my question.