I watched a video a few years ago where one of Kent Beck, Martin Fowler, Jeff Sutherland, Ken Schwaber, I don't remember who exactly, explained what they wanted to do with the Agile Manifesto, what screwed up. He explained that they wanted to give guidelines, not a strict rules. They wanted flexibility. But people started selling this as courses, business, rules. Some Agile practitioners become fanatics on the topic. And this created misunderstanding and chaos :D

For 20 years, I have seen it working and not working, and the reasons are a lot. It can be affected of level of expertise, quality of documentation, pressure from management, engagement of the clients, etc.

Simple example of failing, and how one of my team overcome it. There is no specification. Option 1: team complains that the specification is bad, and this makes the code quality bad. Option 2: the team pro-actively prepared the specifications, gave them to the client for approval. Writing the specification was, a kind of, added flexibility, that was introduced in the sprints.

Another example, why should the sprints be fixed at 2 weeks. Sometimes, people try to finish for two weeks and they produce bad quality code, because they are time pressured. Be flexible and make them 3 weeks, if the sprint includes things like, preparing specifications, or if the sprint includes pauses for bug fixing. :)

So it is not the Agile that makes the project successful, it is the people. Agile just help for tracking where you are , and what you need to do ;)

Now with AI, you can use Agile again, there are agentic frameworks that support it and they give good results, in my opinion. If the people use it wisely, think what they do, and try to do things better, it will work. Of people are lazy, don't know what they are doing, don't have expertise on software development, it will fail :)