As @ranoncles said earlier russia isn't spain but even more importantly the Russian elite (which is the only class that maders in this context unlike in Britain or even france) never had great moral during OTL, St. Petersburg was practically a gost town sense all the nobals fled before borodino was even fought. Its hard to see Alexander not making peace after losing his army that badly.What would winning in Russia look like?
Sure, given a bit of luck he could inflict a smashing defeat on the Russian *Army*, but so what? He inflicted lots of crushing defeats on *Spanish* armies without achieving a thing, The Spanish just pulled themselves together and went on fighting. Why would the Russian be any different?
There's been much natter about restoring the PLC, but how exactly could that be done? The old Grand Duchy of Lithuania is a vast area stretching from Riga to Odessa., and with nothing much in the way of natural defences. Nor have its inhabitants - mostly Ukrainian and Belorussian peasants, any reason to be loya to their Polish landlords, How long would such a state last one the Tsar had raised another army.?
Not that that means the plc was coming back (Although I doubt the Russian elite would be to torwn up about losing taratory it had held for less then a decade) napoleon was much more interested in getting russia back in the CS then in polish ingrandismint.