Kiev was capital of Kievan Rus', which is a different entity than the Grand Duchy of Moscow which later became Russia.

Russia is named after the Rus people...

Ukraine literally means 'border'...

> Ukraine literally means 'border'...

So, Russians are not aware of Slavic languages, where 'Kraina' (as in Ukraina) means country?

Don't know your point but https://en.m.wikipedia.org/wiki/Name_of_Ukraine

As a native speaker I can assure you that the ukrainian word Krai (край) has two meanings - a land and a border. But border only of a physical thing - of a cup, table or watch. Never as a border of a country (or geo-social area), for this we have a different set of words (кордон, межа, границя)

Ukraine means border, but I'm not sure if you know which country border (hint: not Russia).

It's like saying that Athens were the capital of Roman empire before Rome.

...which sounds like something that every Greek person would agree with, without even an iota of doubt or shame. Some of the Greek-Americans I have known actually have said exactly that, spontaneously, and completely independently of one another.