No it's not. This has always been a needlessly iconoclastic rather than sensible suggestion.
At the very least it is not once you're working at the wrong kind of scale.
Once you have an awkward number of customers (more than five and less than a hundred), maintaining duplicated code that should have been abstracted and modularised will only seem cheap if you don't mind that you burn through even junior employees at a pace.
And in the LLM era the wrong kind of scale appears in different ways; code generated and duplicated without proper abstraction and then maintained by an LLM that cannot be trusted to do the same modification each time it encounters a pattern or to have enough of an overview to slowly rescue duplicated code through good abstractions.
I would go as far as to say that any abstraction you can maintain (that is in active maintenance, I mean) is better than code duplication once you are past a de minimis threshold.
At the very least it is not once you're working at the wrong kind of scale.
Once you have an awkward number of customers (more than five and less than a hundred), maintaining duplicated code that should have been abstracted and modularised will only seem cheap if you don't mind that you burn through even junior employees at a pace.
And in the LLM era the wrong kind of scale appears in different ways; code generated and duplicated without proper abstraction and then maintained by an LLM that cannot be trusted to do the same modification each time it encounters a pattern or to have enough of an overview to slowly rescue duplicated code through good abstractions.
I would go as far as to say that any abstraction you can maintain (that is in active maintenance, I mean) is better than code duplication once you are past a de minimis threshold.