Every darkroom has a distinct personality of its own - just as most of the other stuff in photography. I've had visitors who are appalled with the light leaks in mine.
One unconsciously compensates ... I probably have a set of learned reflexes that I follow that allow me to produce good work (before anyone starts -- yes, to ME) in spite of the light leaks. If I worked in a darkroom without them ... it is different ... and I would have to work differently to get back to the same place.
I'm a little surprised that no one here has mentioned "sequestering agents" - chemicals added to commercial developers to compensate for impurities in the water used to mix them. There was a discussion, many moons ago, where some suggested that distilled water was not a good thing in all cases, as the "sequestering agents" would have nothing to act upon, and therefore the overall performance of the developer would be, actually, reduced.
I think that the most important deal in processing is not "perfection", but "stability." As long as things do not change we can learn to deal with them. Moving targets are tough.