Or is it they just didn't go far enough with the modularity you specifically wanted?But 5E just gave up on modularity.
You basically said they have Flanking, but its too powerful. So the 4E module is there... but it just didn't match the numbers you felt it should have to be good. You needed the book to have written down as an option "Flanking is a +2 to attack" in addition to the Advantage/Disadvantage version. Likewise, you needed the book to specifically state a module of something like "A Short Rest can be 5 minutes and a Long Rest be 8 hours" so that it could match your desired preferences, rather than only the 1 hour / 8 hour base version or 8 hour / 1 week variant that it says.
That specificity though to me is just matters of degrees. The module to add in those 4E-isms is there... but they just don't match 4E exactly and instead use 5E-isms in their place (like Adv/Disad instead of small numeric bonuses.) The essence of the edition is there, it just doesn't go far enough for your tastes. Which is cool... I have no issue with that. You want what you want and it is what it is. I would just disagree that a module that doesn't far enough is the same as a module that doesn't exist.