Not to mention, most datasheets will include calculations for selecting components where the value matters, e.g. maximum current from a pin, threshold of an enable, etc,
I've been bitten by a few example circuits before, e.g. a 3.3-5V level shifter, in the diagram it had the enable pin driven on the 3.3V side, but the minimum input for logic high was 3.7V. which meant a bodge to test and a respin.