With capitalism, the concept ofin the domain of capitalism, excessive consumption has become soa crucial issue in society.

You can say "such a crucial issue" or "so crucial in society," but "so" + adjective + noun does not work. "With capitalism" is OK but sounds slightly odd because it leaves it unclear what the relationship of excessive consumption is to capitalism; "within" would be a better preposition to use

Especially in developed and developing countries, this situation brings many positive and negative consequences.

"Excessive" in the previous sentence implies you are focusing on negative consequences, thus "positive" here is sort of contradictory

Accordingly, while many people think that consumerism has manyits benefits, like the economic development of countries, it hasleads to more harms than advantages.

I just replaced with "its" to avoid repeating "many." I think "leads to harms" sounds more natural than "has harms"

In my opinion, overconsumption causes irreversible damage to the world we live in and individuals are adversely affected financially and psychologically.

"cause damage TO"

First of all, the most importsignificant result of excessive consumption is to cause irreversible damage to the nature.

I think "significant" is better, because "important" has a slightly more positive connotation that clashes. "Nature" when referring to the natural environment, doesn't take "the"

As aThe result of this, it meanis the destruction of our natural resources and leaves an unliveable world for future generations.

"As a result of this, it means" is a little awkward, I suggest this instead

Studies by the World Wide Fund for Nature show that in the next 30 years, almost 80% of water and food resources will be depleted due to excessive consumption.

To give an example, many situations such as the increased cutting moreof trees, uncontrolled consumption of water resources, and buying of products which we do not need, lead to air pollution, depletion of natural resources, and also the destruction of nature.

"situations such as the the cutting OF trees," "buying OF products" etc. This is a more formal structure but more correct in writing

On the other hand, excessive consumption affects negatively affects not only nature but also people.

The fact that people buy more products than theiry needs causes to bring leads to serious financial difficulties.

"cause to bring" isn't used, use "lead to"

It has been seen in the news lately that many people have psychological diseases due toconsequences resulting from their credit card debts, and even suicide rates are increasing according tos a direct result of this situation.

Or "the news lately has highlighted that" also works and is simpler. "Diseases" is maybe a bit strong in this instance because it makes it sound like they're developing schizophrenia or something from credit card debt, I would rather say "psychological consequences" even though admittedly, this may sound like downplaying the consequences (up to and including, as you say, suicide)

In conclusion, although some people consider that consumerism is so important for the economic development of states, the drawbacks of excessive consumption should not be ignored.

you could say "very important" (although frankly it's redundant and I suggest just "important") but "so important" doesn't really work here; my sense is that using "so" as a synonym for "very" in this way is too informal for this type of writing

Otherwise, all natural resources will be used up and our world will become uninhabitable.

It should not be forgetotten that leaving a goodhealthy world to the next generations is one of ourhumanity's greatest responsibilities as human.

Forget (present tense) - forgot (past tense) - forgotten (past participle): It is forgotten, it should not be forgotten. I would say "good" is too vague to describe world, "healthy world" is better given the context. "greatest responsibilities as humanS" would also work, though "humanity's greatest responsibilities" is probably the most common formulation for this