Very good of you to remind us about the manifesto! Now I think backlog grooming is useless https://agilemanifesto.org
Thx! Or even more correctly, Manifesto for Agile Software Development, but even that term I'm sure can become abused and perverted by adverse incentives.
I have been on two major software projects (among others) that went horribly wrong. One used waterfall methodology and the other Agile. No process will save you from bad ideas and decisions. The Agile priests I have encountered will try and convince you otherwise.
In other words, statistically far more likely to be successful for the majority of companies over the long term than the alternatives?
Whether or not it's part of the manifesto, or is some combination of some other methodology, you can do nothing else but the daily update + a demo with the customer every week and you will be far ahead of many companies. One of the companies I did work for way back _just_ released a product of mine. This product was written and completed in six months ~8 years ago. My team did it using an agile process, the rest of the company uses waterfall. They made no major updates to it since it was created. A product at that same company that was started 2 years BEFORE my project is still not finished.
The problem we ran into with the last big Agile project I was working on was the customers were the product owner and internal stake holders. Every two weeks, a demo would occur and we were praised for building what they wanted. The problem was what they wanted was a flawed idea.