In times of authoritarian and fascist uprising, I think we should be careful what ideas we spread. The telling of a "German" or "Russian" people that are "natural" ethnicities is not far from right wing ideology. Why would you even use "Germans" and "Germanic people" synonymously? That's anachronistic and they don't really have anything to do with each other. Some Germanic people also lived where Ukraine is now btw.

It isn't even clear if "Germanic peoples" existed as a distinct group of people:

Different academic disciplines have their own definitions of what makes someone or something "Germanic".[3] Some scholars call for the term's total abandonment as a modern construct, since lumping "Germanic peoples" together implies a common group identity for which there is little evidence.[4] Other scholars have defended the term's continued use and argue that a common Germanic language allows one to speak of "Germanic peoples", regardless of whether these ancient and medieval peoples saw themselves as having a common identity.

Oh, and the Nazis did synonymize both Germans and Germanic peoples as well:

The publishing of Tacitus's Germania by humanist scholars in the 1400s greatly influenced the emerging idea of "Germanic peoples". Later scholars of the Romantic period, such as Jacob and Wilhelm Grimm, developed several theories about the nature of the Germanic peoples that were highly influenced by romantic nationalism. For those scholars, the "Germanic" and modern "German" were identical. Ideas about the early Germans were also highly influential among members of the nationalist and racist völkisch movement and later co-opted by the Nazis. During the second half of the 20th century, the controversial misuse of ancient Germanic history and archaeology was discredited and has since resulted in a backlash against many aspects of earlier scholarship.

To synonymize "Russians" with "Slavic people" is also wrong, as Slavic people where a diverse group of very different people living in a different regions of the world. We also don't know where the early Slavic people lived exactly.