Sometimes it works, sometimes it doesn't. It worked in the Napoleonic Wars and World War II, however in World War I the citizenry eventually got to the breaking point as their sons were sent into the meat grinder and overthrew the Czar. Then in Afghanistan the Russians ran into an opponent that was just was willing to throw endless hordes into the meat grinder as they were, so eventually just gave up in frustration.
“Well, it’s sustainable if you understand the Russian mentality for fighting wars. Basically, they throw endless hordes of soldiers into the meat grinder with no real concern for losses.”
Sadly, you are absolutely correct.