Youths and young people

These days youths are more challenged by the future because making decisions about the future is not easy.

This is grammatically correct but inappropriate.

The countable noun youth tends to have negative connotations, especially when it's plural:

Youths at football matches often cause trouble.

Youths are troublemakers, at that awkward age between childhood and adulthood when they rebel against authority and indulge in sex, drugs and rock and roll, often with negative consequences.

Youths hang around town in gangs and old ladies are afraid of them.

The lexical phrase the youth of today is also usually negative:

The youth of today have no respect for others.

Positive about young people

Most of the time in IELTS Task 2 essays you want to maintain a more positive - or at least neutral - attitude to young people, and so it's probably best to refer to them as exactly that - young people!

These days young people are more challenged by the future because making decisions about the future is not easy.

Another option for IELTS writing would be:

These days the younger generation are more challenged by the future because making decisions about the future is not easy.

In IELTS Task 2 you also often want to make a prediction about how a situation may affect young people in the future. In this case you are talking about future generations:

Global warming is a problem that governments need to solve for the sake of future generations.

Future generations will prosper as long as they follow a healthy lifestyle.

Notice that we assume there will be more than one future generation and if we're generalising then there is no article (the).