[whistle] in the wind

to make a fruitless attempt to solve a problem

The idiom "whistle in the wind" is believed to have originated in the United States in the early 20th century. The phrase is used to describe a situation where someone is speaking or making a statement that is unlikely to be heard or acknowledged, or where someone is making an effort that is unlikely to be successful or noticed.

If we don't have a solid plan in place, our efforts will be like whistling in the wind - we won't achieve anything meaningful.
The company's attempts to enter the market without doing proper research were like whistling in the wind - they were bound to fail.
The protestors are shouting slogans, but it's like whistling in the wind - the government is unlikely to respond to their demands.
Trying to convince the stubborn client to change their mind is like whistling in the wind - it's unlikely to have any effect.