Thanks so much!
And I'm happy to answer your question!
Personally, in my 1,5 years as a concept artist I haven't had to write any long texts at all, except for answering emails etc. I got the job I have at Atomhawk based purely on my portfolio. Aka my art skills. Still, I'm sure knowing how to write an essay can come in handy sometime, but at the end of the day, what matters most is the art skills if you're looking to work as a concept artist.
Hope that helps, and good luck with your essay