I find this really interesting because this is similar to how human judgement works. Say the gods represent individual human ideals, then something loved by one person could be pious to them, but impious to another. Like in politics. One person could believe that say the death penalty is a just and right thing, but their friend or neighbor could think it is cruel and unusual. So then the definition of pious is similar to the definition of good, it can differ between persons.

I might be taking things out of context here, but I find the description of "good" interesting here. Socrates describes good as an idea that can still be perceived by the senses, like light. However, ideas are also things that exist in the mind. So doing something good can also be an opinion, but we perceive it as a possible physical manifestation of the action. And possibly there is say, a little voice in your head telling you that you did something good, so we sense that an act of good was done.