Losing thousands (possibly tens or hundreds of thousands) more soldiers forcing that.
Playing macho may seem cool from your chair, but if Ukraine could force that without significant losses, it would already have by now.
Their behavior also shows that they don't see their victory as that close and certain. Even though the statement itself is by a stronger side definitely, unlike in the first few months since the war started.
Ukraine itself is not a "genuinely pluralistic democracy" despite appearances, it's almost as corrupt and authoritarian as Russia.
It's not the case where only Russia has to become more democratic cause democracies usually don't fight each other.
But for Russia to stop being a threat it's sufficient to just lose this war finally. It won't recover its ability to attack anyone anytime soon, and when it will, the process of recovery itself is going to naturally ensure that it's not interested in attacking Ukraine.
So yes, you are right about oligarchs and the general structure of the societies.
Essential assets you are talking about are what exactly? If you mean factories and plants, then actual equipment in most of them was obsolete even in 1991, and through the 90s and 00s has mostly been scrapped.
There are some remaining and even functioning, yes, but whether state ownership is going to prevent those from slowly crumbling due to growing obsolescence, irrelevance and lack of expertise, I'm not sure.
Basically industrial capacities are something to be created from scratch mostly.