In a world where technology has been considered the core of every country's development, any expression of human creativeity, such as art, has been relegated to the background.

Some people think that, art is therefore, art is not inessential anymore.

Or you can say, "Some people think that art is thus inessential."
It is possible to include "therefore" at the middle or towards the end of a sentence however, it is more common to find it at the start of a sentence. Putting it at the end can be a stylistic choice to make your writing sound a little more formal/academic.

I do not agree with this view, and I believe that art is still very important for a society.

To begin, art is a way people can express their feelings, and i. It helps them to understand themselves better, which is essential to treatfor the treatment of mental health problems or traumas.

For example, with rock art, we are able to appreciate how the human beings related to each other and with nature many centuries ago.

They did not have the tools we currently have to paint, but they used their hands to draw some animals and recreate some scenes.

In conclusion, I think art helps us to express and connect with our feelings, and. It also it carries a historical significance and helps us to understand our past.

In a world where technology has been considered the core of every country’s development, any expression of human creativeity such as art has been relegated to the background.

I’m not entirely sure whether or not “every country development” would be right, but “every country’s development” definitely sounds better.
“Creative” is an adjective, but “creativity” is a noun

Optional - “relegated” isn’t really used much, so while it is right, a more common word might be “pushed” as in “art has been pushed to the background”, or you would also say something like “art has been disregarded”

Some people think that, therefore, art is not essential anymore.

Optional:
“Therefore” is put at the beginning of a sentence more often (Therefore, some people think that art is not essential anymore).
You could also use “important” or “significant” instead of “essential”, as to me essential implies that the thing is required/mandatory, and in some cases is even required for survival.
You could also replace “not… anymore” with “no longer…”. As in “art is no longer essential” instead of “art is not essential anymore”, which would be a more natural expression.

To begin, art is a way people can express their feelings, and it helps them to understand themselves better, which is essential to treat mental health problems orand traumas.

Optional - could replace “to treat” with “for treating”
Replacing “or” with “and” at the end sounds a bit better (“or” can imply that it is only one or the other that is treated through artistic expression, whereas “and” implies that it treats both)
“Trauma” usually stays as “trauma”, regardless of if it is intended as plural or singular.

Painting, drawing, or even making dolls are ways people can use to communicate what they think or feel.

If you wanted to say “to use”, then it would be better to say “are things that people can use to communicate”

For example, with rock art, we are able to appreciate how the human beings are related to each other and with nature many centuries ago.

“Human beings” because you’re talking about multiple people.
You would say “are related” or “relate”, but never “related” by itself (or not that I can remember). “Are related” is used more with how people are connected (sometimes as family), while “relate” would be used more so in the case where someone feels/knows what another person is going through (as in the person relates to the other).

They did not have the tools we currently have to paint, but they used their hands to draw some animals and recreate some scenes.

They used more than one hand (and each person also almost undoubtedly would’ve used two hands too), so handS. “Some” isn’t really necessary in either part at the end, and it sounds a bit more natural not to use it.

In conclusion, I think art helps us to express and connect with our feelings, and it also it carries ahas historical significance toin understanding our past.

The original sentence was good too, but this makes it feel more natural.

In a world where technology has been considered the core of every country development, any expression of human creativeity, such as art, has been relegated to the background.

STherefore, some people think that, therefore, art is not essential anymore.

I might be interpreting your original sentence wrong though.

I do not agree with this view, and I believe that art is still very important for ato society.

Me too!

Painting, drawing, or even making dolls are all ways that people can use to communicate what they think or feel.

They did not have the tools we currently have to paint, but they used their hands to draw some animals and recreate some scenes.