Literally everything you’ve stated is false. Every statement.

A) Lots of Russians died during WW2, it wasn’t “evil Russia sends troops from occupied republics to fight for them while Russians sit back”.

B) Lots of mercenaries from post-Soviet republics fight for money on Russias side now

C) Russia didn’t pull out because they’ve run out of men. Where did you get this?

Of course many Russians died too. But the bulk of the casualties were Soviet soldiers from the Asian republics.

There are a couple of good WWI documentaries on YouTube which you can watch for free. You'll find that C) is the truth.