The steppes are at least nomadic, Germania, the Balkans, Eastern Europe are very habitable, this meant the people there could grow to large populations and actually change the demographic and linguistic makeup of Rome if they invaded.
The steppes produced better soldiers and also they could create massive armies. Now and then they built a military superpower. Cannot say the same of the Germans, where the Romans tended to face many small armies of Germans. Also what is interesting is that a pattern developed when the steppes put pressure on the Germans pushing them into Rome. In the process, the Germans were taking the first hit.
That's why the Germanic migrators didn't just pull a Qing and stay at the top, there were enough of them to dominate the area in force and so they didn't just completely assimilate into Rome, they fundamentally changed each of the areas
Some truth to this but at the end, the Barbarians adopted the Roman religion Christianity, Roman philosophy, generally the Roman language which became French, Italian, etc. The fundamental difference is that for some reason unlike in China, once Rome fell apart, it never pulled itself together.