Except "real morality" is also anything but consistent. There are some things that we're pretty universal on. But there's a lot of flex. There are some people that believe you're evil for having certain sexual attitudes. There are some people who think any sexual desire whatsoever is evil. And different cultures determine ethics and morality on vastly different core values and axes.
If we consider that Larian is a studio from the Western Hemisphere, we can assume that this set of contemporary morals is applied into the development of the game, which is hinted at by the fact that we can, for example, romance any race or gender. This has been the case for the predecessors and many other RPGs as well. Social structures and the culture might differ, but the PC is generally disconnected from that and/or is participant in reshaping that structure accordingly (like in the trope where the PC helps villagers overthrow the feudal rule of a greedy lord, or the general easy access for the PC to all parts of the society and culture). Many universal morals have been true and unchanged for many, many years and worldwide, too. This does not mean that differences or opposition does not exist in-game or in our contemporary society, but that these are statistical outliers, aided by the fact that there are social, professional and personal consequences for not complying.
This however is something the game (and many games at that) severely lack. Only when there are no consequences moral flexibility is really a thing. That is why evil or "pragmatic" actions are much more prevalent in games.
