It's a waste of time and energy.

那是浪费时间和精力。

《牛津词典》

"It's a waste of time," he concluded.

“这是浪费时间，”他最后说道。

《柯林斯英汉双解大词典》

Personally I think it's a waste of time.

在我看来，我认为这是浪费时间。

《柯林斯英汉双解大词典》

Getting beat at Wembley is far worse than getting dumped out in the third round as it's a waste of time getting there.

BBC: Kevin Ratcliffe

If you have a theory that either, you know, is part of your case or part of your defense against charges by the government and there's no legal support for the defense, it's a waste of courtroom time to have a parade of witnesses.

NPR: What Does Watada Case Mean for Military Law?

But at the end of the day, it's basically a big waste of time, not to mention slow to use.

CNN: ASIANOW - TIME Asia | Letter from Japan: Whale of a Problem