It would seem that from the perspective of the West and most of the world, the Ukrainian War has been much more successful than Vietnam:

1) Its already put Russia in its place, sending a message that they can't take whatever they want.

2) It has seemingly scared China into more or less backing of the Wolf Warrior thing (they're seeing the alliance and economic power of the West? The willingness to fight for Democracy?) Their "partner" Russia is embarrassing them?

3) It is showing that Putin's economic cards (ie oil) aren't as powerful as he thought.

That said, I believe you're right that the West needs to further commit, for fear of wearing out the Ukrainians. I don't really see why NATO doesn't fully take in Ukraine, at least blockade the Black Sea, achieve full air superiority over Ukraine (Belarus and any other place from which Russia is launching missiles). Yes there's the threat of nuclear escalation, but I believe Putin knows he's outgunned there, possibly a prelude to a NATO favorable truce. There are forces to the right of Putin, and he'd be smart to play ball at some point to save his hide, he can pick on the Chechnya's if he wants.