To criticise something as bad, without value, or unnecessary. (Cambridge Dictionary)
To depreciate (something, such as a coin) officially or publicly. (Merriam – Webster)
To express strong disapproval of. (Merriam – Webster)
To speak disparagingly of; denounce as faulty or worthless; express censure of: (Dictionary.com)
To condemn or depreciate by proclamation, as foreign or obsolete coins. (Dictionary.com)
If someone decries an idea or action, they criticise it strongly. (Collins Dictionary)
Publicly denounce. (Oxford Dictionaries)
Examples
Protests, vigils around US decry white supremacist rally in Charlottesville.
https://www.timesofisrael.com/protests-vigils-around-us-decry-white-supremacist-rally-in-charlottesville/
Sewage, violence and sexual abuse: NGOs decry grave conditions at the Moria refugee camp.
https://hellasjournal.com/2018/09/sewage-violence-and-sexual-abuse-ngos-decry-grave-conditions-at-the-moria-refugee-camp/