You have omitted the fact that vitamin K2 is produced not just by bacteria fermenting our food before we eat it, but also by bacteria in our intestines. Have you researched this source of K2? Do you have any reason to believe intestinal flora does not produce enough K2?
At university I was taught that vitamin K deficiency is extremely rare due to its production by inestinal bacteria and that is why normally only newborns (who simply don’t yet have gut bacteria) receive K2 supplementation.
I don’t think that my argument about bacteria being a source of Vit K2 is alone sufficient for arguing that we are commonly insufficient in it. The argument however makes it plausible that we get less of it then in paleo times.
My main reason is that it seems that people who take a lot of Vitamin D3 but no Vitamin K2 show symptoms that correspond to Vitamin K2 deficiency and as a result it’s prudent to suppelement K2 when supplementing Vitamin D3 seriously.
A lot of K2 research also happened quite recently and our existing system of thinking about RDA unfortunately treats substances as being independent from each other which makes things harder.