But then libertarians like to change things too, but in very different ways to what you'd approve of if you identify as left/progressive.

So it's not that simple.

There will always be a spectrum of opinion and values, and people will always try and simplify it down to a "left" and a "right" wing, and it won't work very well but people will insist on doing it anyway.

For what it's worth I don't believe it's genetically hard-coded; it's as much adaptive to culture and responsive to what people see happening in their own lives and in the world around them.

The problem with this definition is that it'd invariably result in a swapping of nomenclatures once one side became dominant. And while we do tend to swap between dominant ideologies on about 20 year spans (roaring 20s, warring 40s, hippy 60s, big business 80s, identity politics 00s, ?? 20s) the nomenclature remains attached to broad ideologies rather than whichever side happens to be dominant.

In practice I think it comes down more to the desired direction of change. Conservatives tend to value pragmatism and liberals optimism. 'If everybody was kind to one another, we could have a utopia so let's work in this direction!' 'People will never all be kind to one another, so let's focus on systems that work even when people engage in bad behavior.' It even has direct parallels in game theory. Do you focus on achieving the max possible (exploitative) system where possible gains are maximized, but so are possible losses? Or do you focus on systems that minimize the worst possible outcome (game theory optimal) but, in practice, also tend to reduce the general case best possible outcome as well?