Do the simplest thing that could possibly work

IMO, the most important thing about this sort of advice (and maybe most advice) is to treat it as a "generally useful heuristic, subject to refinement based on judgment" and not as an "ironclad, immutable law of the kingdom, any transgression from which, will be severely punished".

Sure, try to keep things simple. Unless it doesn't make sense. Then make them less simple. Will you get it wrong sometimes? Yes. Does it matter? Not really. You'll be wrong sometimes no matter what you do, unless you are, in fact, the Flying Spaghetti Monster. You're not, so just accept some failures from time to time and - most importantly - reflect on them, try to learn from them, and expect to be better next time.