a waste of time

基本解释

Attempting to change someone is a waste of time and energy.
尝试改变别人是一件浪费时间和精力的事情。
At the same time, other students in the same class already have the skill down cold, so further practice for them is a waste of time.
同时，同一个班级的其他学生可能已经熟练掌握了这项技能，所以继续练习对他们来说只是浪费时间。
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An architectural description, like any deliverable, needs to be created for a purpose and an audience, otherwise creating it is a waste of time.
一个架构描述，如同任何可交付的产品，是需要为了某个目标和受众而创建的，否则只是浪费时间。

In addition,news agencies provide updates and companies share product information through Twitter Some critics say Twitter is a waste of time that takes people's attention away from their work.
I think it's terribly important to keep the distinction in the back of our minds even if we find it, in practical terms, well nigh impossible and possibly even in many contexts a waste of time to be perpetually enforcing it.
你们一定要牢记这个区别,这实在是太重要了，尽管有时我们发现在一些的文本中这种区别很微小,看上去不值得花时间去研究或使用。
耶鲁公开课 - 文学理论导论课程节选
The last one that we saw was a complete waste of time.
我们看的上一部这种电影完全是浪费时间。
There is no 实战 - SpeakingMax英语口语达人

To call a business plan a waste of time seems a bit heavy handed.
FORBES: Why Business Plans Don't Work And 'Pivoting' Is Nonsense