Why do some developers consider Agile development to be nonsense?

(1) Company decides to devote resources to a feature.

(2) Developer writes code and submits patches upstream (e.g. to the Linux kernel).

(3) Upstream takes some indeterminate amount of time to get patches into a release.

(4) Company defines a downstream (i.e. commercial) release based on a particular upstream release.

(5) The possibly-pristine but also possibly-unrecognizable code from (2) is pulled from the upstream release into the downstream tree.

(6) More testing, debugging, tweaking, etc. on the downstream tree yields an actual release.

Just in (3) we see one part of the problem: upstream quite likely isn't agile/scrum themselves. Often they don't care about a particular vendors' release schedules; if they do, then someone would argue they're "dump and run" fake open source, and not a true independent upstream. They're almost certainly not going to give a crap about sprints or story points or anything else about the local agile/scrum process. These methodologies pretty much don't work unless everyone is completely committed, and with separate upstream/downstream that's just not the case.

Even with everyone on board, the disconnect between (2) and (4) is a problem. Pushing code upstream and pulling it downstream are two separate tasks, even if they're done by the same person, and there's this big gap between them. At best, this makes scheduling more complicated. More often, it makes agile/scrum style fine-grain scheduling and tight coordination impossible. Measuring "velocity" and all that isn't possible when there's so much externally imposed variability.

For something that's long term and systems-oriented and open source, these methodologies are practically useless. Actually they're worse than useless, as they misdirect effort and interrupt useful work. YMMV.

Guess what? Those things are still meetings. They still take up actual time that could be spent on getting shit done.

Back when I was a wee lad, with nary a keyboard callus upon my digits, I learned about a little thing called Murphy's Law. In brief, it says that if anything can be done incorrectly, someone will eventually do it that way. It was a warning to those designing things, to make doing the wrong thing impossible, or at least much more difficult to do accidentally.

As a result, among those taught about Murphy's Law, "doing it wrong" was a design flaw. If, for instance, you could destroy radio reception in a handheld device by holding it in a particular way--a way that did not cause pain or discomfort in an ordinary human hand--it was the fault of the device manufacturer, not the user.

If you can do Agile "wrong", then it is a problem with Agile.

As for myself, I just think to myself that someone, somewhere, has weaponized an idiot, and has launched it against me. It is equal parts Inspector Clouseau, Mister Gumby, Ali G, Drunken Master, and a particularly evil djinn. He will do exactly what you ask, in the most malicious manner possible. He will follow a process with absolute rigor, and produce the worst possible outcome.

I firmly believe that such people actually exist--individuals so brutally incompetent that they are indistinguishable from malicious trolls. So you might as well plan around a person intentionally trying to break your design while still maintaining the plausible deniability of not breaking any of your rules.

Agile cannot hold up under the assault of a weaponized idiot. There are simply too many possible attack vectors.