Up until 2 or 3 years ago, you could directly travel by night train from my (relatively minor) home town Freiburg to Moscow. There are direct trains from Paris to Freiburg or Frankfurt (where the night train also stopped), so this could've saved the layover in Warsaw.

https://www.bahnbilder.de/1200/wlbm-172-am-ende-eines-777062...

Note that there are already regular freight train connections from Duisburg, Germany to China:

https://upload.wikimedia.org/wikipedia/commons/8/8f/Trans-Eu...