As we can see from this essay, which was written a very long time ago, the retort 'keep it simple' has a long history in AA. Sometimes there is unnecessary complexity, and a simple solution is best.
Sometimes, however, progress or effectiveness can be confounded by excessive simplicity. The Step Four in the Big Book is rather an involved affair, for instance. One could cry, 'keep it simple!' and avoid the whole matter. Similarly: the pains-taking of Step Nine, or the chapter after chapter on Step One in the Big Book. Surely those could be 'kept simple' too? 'Are we not frightening off newcomers and making a mountain out of a molehill?' Such arguments, experience suggests, are silly. If I had heeded such cries, I would likely not be sober today.
There are times when more simplicity is required; there are times when 'keep it simple' will obscure the truth and stifle good ideas.
I have caught myself using the phrase with others, when what I really mean is, 'I disagree with you', 'that's not interesting to me', 'I don't find that useful right now', or even 'I'm lost'. Like the proverbial dog in the manger, I have then sought to shut down the discourse, because it is not to my taste, citing this slogan: 'keep it simple', as my authority. Often, I have not even properly examined the subject matter in question. 'Keep it simple' can sometimes be the AA way of saying 'TLDR' ('too long; didn't read').
This slogan, like any other spiritual principle, is not a trump card. As has been wisely said, 'to a man with only a hammer, everything looks like a nail'. I'm cautious about using the phrase now: does it actually apply in this situation? Or am I simply being presented with a conversation or a proposition I do not personally care for? I've learned, in the case of the former, to argue my point coherently, rather than slapping down the slogan, as if I were ringing a time-out bell, and in the case of the latter, to keep my big, fat mouth shut.