Flogging a dead horse
This simile describes attempting to get more out of something that cannot give more, or to attempt to arouse fresh interest in something that is either hopeless or already settled. E.g. "There's no point in continuing with this as you're just flogging a dead horse."
Why it matters
This language may not be inclusive of vegan colleagues as it references violence against non-human animals. Veganism is recognised as a philosophical belief and is protected by the Equality Act 2010.
Instead try saying:
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