I’m just repeating what happened or what the plan was the last couple of go arounds, with Napoleon and Hitler.
Napoleon did occupy Moscow, but it didn’t help him very much.
Hitler was turned back just short of Moscow, but the Russian government had all sorts of continuity plans that involved moving further east. Entire factories were uprooted and shipped into the Urals.
None of the current ICBM platforms were designed for missile defense. Missile defense simply did not exist at the time.
Sentinel is busting its budget because it’s renovating and rebuilding all of the ground segments: all of those decrepit silos and computer systems. It’s still money well spent in my opinion.
Missile guidance is not a computationally hard problem, and it hasn’t changed much since the 50s. Terminal missile defense is a fantastically hard problem, and wasn’t mastered until the last decade or two. And the current generation missile defense capabilities still haven’t all been demonstrated in combat.
Having said that, I would generally expect NATO’s missiles to work as advertised in a hot war. And I would plan for Russia’s missiles to be somewhat less effective than they advertise, but still a credible threat.