A brain, a manual and google is usually a pretty good way generally to make solid decisions, respect the limits of your chosen stack.

What happens when there is >1 brain involved... or when brainless, manualless decisions eventually get made... or two pivots from now...

I'm not disagreeing with your approach. I agree with it, especially as starting point. I'm cautioning that resilience against complexity isn't about how easy it is to make good decisions when you understand the spec, read the manual and calmly proceed. Complexity and fragility accumulate when one or all of these are absent. How easily you can (and thus inevitably will) make a mess... not how easily you can keep it clean.

IRL situations with regular rdbs, a very common trend seems to be long term drift between schema and spec. The flexibility and approachability of postgres often enables a lot of kludge eventually.

Data stores have this dichotomy between "look how easy" and "is limiting factor" that speaks to difficulties we don't know how to articulate or isolate.