"You aren't doing it right" is a valid argument when "it" is well defined. No True Scotsman is a fallacy of ambiguity—it occurs when "Scotsman" isn't well defined, allowing somebody to continually move the goalposts in response to an argument.
In the case of Agile, Scrum, and retrospectives, they all have published definitions, so No True Scotsman doesn't apply.
Are you valuing processes and tools over individuals and interactions? You aren't doing Agile right. (Agile Manifesto)
Does your team not consist of "one Scrum Master, one Product Owner, and Developers [with] no sub-teams or hierarchies [who] internally decide who does what, when, and how?" You aren't doing Scrum right. (Scrum Guide)
Does your retrospective not include "Decide what to do?" You aren't doing retrospectives right. (Agile Retrospectives book.)
In fairness hardly anybody does these things right, so it's tempting to lob No True Scotsman criticisms. But that's just as fallacious. A more accurate criticism might be to say that Agile & co. are too hard to do right, or to say that they require a business environment that doesn't exist in most companies.
I can't help being amused by this comment, which seems to to be arguing:
"This isn't a One-True-Scotsman fallacy, a true One-True-Scotsman fallacy would be <insert narrower definition>, your claim about this fallacy is fallacious"
I'm pretty sure Agile, Scrum and Retrospectives have multiple published definitions, both broad and narrow.
Sure, I can see the irony. On the other hand, your interpretation of my argument is absolutely correct. I'm saying that people in this thread have gotten two things wrong:
1) They don't understand Agile, Scrum, or retrospectives, each of which have authoritative definitions (which can be found at agilemanifesto.org, scrum.org, and in the Agile Retrospectives book).¹
2) Furthermore, they don't understand the "No True Scotsman" fallacy.
Correcting a misunderstanding is not "No True Scotsman." If somebody called a car a "horse," and you said, "that's not a horse—a horse has hooves, not wheels," would that be No True Scotsman?
¹You could argue that those definitions are overly broad, or fuzzy, or many other things. But that's not what people in this thread are doing. They're saying horses have wheels, then saying it means horses can't jump.
In the case of Agile, Scrum, and retrospectives, they all have published definitions, so No True Scotsman doesn't apply.
Are you valuing processes and tools over individuals and interactions? You aren't doing Agile right. (Agile Manifesto)
Does your team not consist of "one Scrum Master, one Product Owner, and Developers [with] no sub-teams or hierarchies [who] internally decide who does what, when, and how?" You aren't doing Scrum right. (Scrum Guide)
Does your retrospective not include "Decide what to do?" You aren't doing retrospectives right. (Agile Retrospectives book.)
In fairness hardly anybody does these things right, so it's tempting to lob No True Scotsman criticisms. But that's just as fallacious. A more accurate criticism might be to say that Agile & co. are too hard to do right, or to say that they require a business environment that doesn't exist in most companies.