I don't disagree with you. The conflict and the consequences are far-reaching and infeasible, with no good way back to normality.

But to Russian autocrats, this conflict is becoming a matter of honor. Putin (and probably his successor) will be committed to seeing this through, until the conflict reaches a state where a peace plan involving territorial concessions to Russia is acceptable to Ukraine and the west. I worry that the conflict will continue (and possibly escalate) for years before we've reached that state. At which point your scenario of insurgency kicks in.