I think the core thesis is that "do one thing and do it well" is about small components that are connected together.
The classic example is shell pipelines, but they are actually quite shit because they only deal with unstructured data (there's finally some work to fix that in Powershell and Nushell but it took many many years).
A better modern example of doing one thing and doing it well is apps that support plugins.
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I think the whole "do one thing and do it well" is terrible advice. A "thing" is not well defined. It's equivalent to "don't have too many features" which of course leads to "how many is too many" and you're on your own.
It's one of those bits of advice like "premature optimisation" that is more often used to excuse thoughtless design than to motivate good design.
The classic example is shell pipelines, but they are actually quite shit because they only deal with unstructured data (there's finally some work to fix that in Powershell and Nushell but it took many many years).
A better modern example of doing one thing and doing it well is apps that support plugins.
----
I think the whole "do one thing and do it well" is terrible advice. A "thing" is not well defined. It's equivalent to "don't have too many features" which of course leads to "how many is too many" and you're on your own.
It's one of those bits of advice like "premature optimisation" that is more often used to excuse thoughtless design than to motivate good design.