You can't compare gigantic Russia with other european countries. Russia has an advantage that is called strategic depth.
It could lead an attrition defensive strategy.
Taking a big city is not necessarily a smart strategic goal. It's' been the same old story since the second punic war. By all standards of the time, Rome was defeated and should have sued for peace on Hannibal's terms.
The big lesson is that there are only 2 ways to defeat on his homeland a country that has both strategic depth and reserves. Either this country accepts that it wants to end hostilities. Or this country is being totally crushed.
Russia un 1812 as Rome after Cannae, did not want to accept peace.
Napoleon did not have the resources to crush a Russia leading a Fabian strategy.
Well, that's an able comparison. As long as Rome stood, Rome which was the capital of the Republic, the Republic didn't sue for peace.
Here, what I meant is as long as they have their capital, they can easily trade space for time.
However, they need a good administrative center. And here my previous analogy with Versailles fails, since Versailles was only ever a castle for nobles, with only highest-level administrative. Paris has always remained the core of French administration, this is why taking Paris is crucial.
Moscow is a large city, with therefore large administration, remnants of the pre- Peter the Great era, and could therefore be used as a backup capital if St Petersburg fell.
Taking Moscow
and Saint Petersburg would probably have brought the Russians to sue for peace, if only to relocate their administration in Perm or Orenburg, or any place that is impossible to reach without ripping one way through all of Russia.