Imagine that there is some group of people that speak English, but never learned to read or write. Someone literate shows up and explains that you can make marks on paper to represent words and read them back. All of the illiterate people are very excited about reading and writing and decide they need to start doing this right away.
Some of the people start learning phonetics and practicing writing the alphabet in order to learn the principles necessary to be literate. It is slow going and very difficult work.
Another group of people start making random marks on paper to represent the words they are thinking in their heads. They stand up in front of each other and hold a book open while pretending to read the pages. Of course they can’t read so they just make up stories. They try their best to emulate all the practices they saw people doing that could read and write.
After a year how do you think the two groups describe literacy? The group that had focused on the principles behind reading and writing would be very happy about it. They can pick up a book and read it. They can communicate with each other by writing on a piece of paper. The group that tried to emulate the practices without first learning the principles would declare literacy a fraud. Both groups would be equally strong in their opinions.
Agile is a set of values and principles. Teams use these to make decisions that lead to good project outcomes. These values and principles guide the selection of different practices.
There are a lot of people trying to “do Agile” by emulating the practices they have seen on other teams. They try to use Scrum, Kanban, Extreme Programming, etc. But these practices aren’t Agile unless they are being driven by the Agile values and principles. Like the people who try to develop literacy by pretending to read and write, they get very frustrated.
Agile is polarizing because it is easy for people to spend a lot of effort doing things that look like Agile without having any of the foundational beliefs in place. If someone says Agile is a recipe for failure, ask them to describe Agile. If they name a bunch of practices and no values or principles, then it isn’t actually Agile that they dislike.