My understanding is biologically, the naturalweaning age of human primate infants is probably somewhere between 4-7yrs, probably closer to the older age.
If a mother or child wean before that age (before the immune system is fully developed, before meat chewing molars have come in) then it’s for cultural reasons. It’s because we’ve invented farming and formula and fridges and routines and “me time” and girls nights out and capitalism and shopping and hobbies and “keeping up with the Jones’” and cities and individualism and fashion and two-income households and standards of living and consumer durables and a million other cultural (not biological) practices that go against natural term bfing.
None of these things are bad (or good) as such - but they represent a cultural norm, not a biological one. Human milk is always an appropriate source of nutritional for human children: it’s our culture that sees it as “icky” or not necessary beyond what we see as babyhood.
So it comes down to personal choice, since we have so many alternatives.
I bf mine to 3 and 4yrs, we weaned earlier than natural term because I was done! That was my choice, made in the knowledge that we have access to good quality food, refrigeration, clean drinking water etc. They would happily have carried on, but I made the choice to stop.