Oh it absolutely will hurt them plenty even if they “win” this war, but the problem is that the more of their strategic aims they accomplish the more emboldened they’ll be. Sure, it’ll take them a while to regenerate their forces (and their demographics being what they are it won’t be easy), but I don’t think that they’re nearly as screwed as commonly assumed.

Russians are no strangers to misery, and the masses are generally more than happy to live with a boot on their necks as long as they believe they have their boots on somebody else’s neck as well. Casualties (wounded or dead) really don’t factor into it, especially considering that it’s the non-ethnic minorities who are dispropotionately getting the short end of the stick in the war – which is how it’s always been with Russia starting from imperial times. It’s a colonial empire but with contiguous borders, and they have no compunctions about throwing minorities in the meat grinder.