The Agile Manifesto was written by 17 very experienced people, so they were thinking in terms of a team of people like them. But today, most software teams have a-lot of people who are only a few years out of college.

Also, today’s distributed architectures make it almost impossible for even an entire team to be able to work across the entire stack of a major digital platform.

In the real world, to maintain complex digital platforms, things are a-lot more complicated than the simple Scrum model. In fact, Scrum does not even fit the situation anymore, particularly if one is maintaining automated integration tests. There are better, more sophisticated and nuanced approaches. I would argue that Scrum really never worked except for a very simple application and no more than a few teams — beyond that, you have to introduce a-lot of other practices to make things work well.