The etymology of Ukraine is the only true thing you wrote. And it's not "libs" that request not using "the", it's the Ukrainians themselves. The Ukrainian language evolved from Ruthenian (and the people used to be referred to that way), which is a whole separate east Slavic language from Russian. Russia conquered them in the 18th century before annexing part of Poland. Belorusians (or Byellorussians) are also a separate people with their own history and language. They largely constituted the peasant class of Lithuania under the PLC.

So regardless of whether it's right or wrong of the USSR to have control of Ukraine or Belarus or any of the other SSRs, Ukraine and Belarus are not Soviet era inventions. They're old, as are the attempts by Tsarist Russia to stamp out and russify them.