There would've been so many advantages to doing this which includes causing Russia to work their way through the entire country before they could possibly take Ukraine down. Another reason is that if Russia was bearing down on Lviv, Poland would be way more interested in helping out their neighbor out of fear Russia was close and would keep rolling their direction. And then guess what? Well, Poland is a member of NATO, so Ukraine would've had major support as a side effect of the agreements NATO members made with each other.
Also, I mentioned this the other day, I wish Ukraine would've cluster-bombed their own highways that Russia had to use. It really would've put a wrench in Russia's plans. It would've slowed their progress, taken out military equipment which couldn't be moved off road, and allowed Ukraine to make a critical decision and that is, should they fly fighter jets and rain down on the convoy.
Then for a psychological edge, I would've torn up the roads towards the end of the convoy but still on Ukraine territory. Russia couldn't turn around their convoy, so they would've been like sitting ducks. It would be like a movie scene where a hero walks into a room of bad guys and then turns around and locks the door. Scary when there's no turning back. It's also scary when an adversary proves they're not scared and are ready for a fight.
Oh well, I'm just an armchair quarterback with no foreign policy experience. It just seems they'd be commonsense moves. God bless Ukraine!