A major European power has invaded a neighboring country. You aggression-is-passé, major-power-war-is-obsolete people are full of it. It's now clear that you're nothing more than industrious tailors to a naked emperor.* In plainer language, your high-falutin theories are rubbish!Um, not so fast. First, this kind of thing doesn't happen very often (which supports us, not the skeptic). Second, the chances of this leading to a major-power war are extremely low (if not zero, then very close to it).
TV pictures of Putin watching military exercises outside St. Petersburg, which I just saw as shown on yesterday's PBS NewsHour (viewed via Youtube), are worth pausing over. Here we have a quasi-authoritarian leader of a country with a sizable military watching, with binoculars, his army's helicopters, tanks, etc. engage in maneuvers. One might almost be forgiven for thinking this was a newsreel from decades ago and that the army was about to roll across some (other) frontier. Binoculars and tanks, however, derive their significance from things one can't see. TV is great at visuals, but even good reporting doesn't always supply the context that visuals require.
In short, you nothing-has-changed-since-Thucydides folks have no reason to crow, because this event doesn't 'prove' anything. To adapt the title of the Stevie Wonder song: you haven't shown nothin'.
ETA: Just saw Dan Nexon's piece on the 'failure' of the 'reset' at Monkey Cage. More on it, perhaps, in due course.
*This phrase is borrowed from the title of Oran Young's 1969 review of a book by Bruce Russett, in World Politics, v. 21, no. 3.