I actually think he did good when he came out in the final, even most people ridiculed him.
The movements were good which a lot mentioned already, and he has a mature understanding of the game; besides the last header all his other chances weren't that horrible as the world made it to be.
The first chance actually was well defending by Upamecano, I mean yea Lautaro might have blasted it in instead of having a touch, but the space he had there normally allows a touch, so like I said good defending by Upamecano, and it was not that bad of a decision by Lautaro.
The second one, it was actually saved by Lloris, even it was given a goal kick, but if you watch the replay in slow motion on the side angle you will see it; Lloris saved it with his right foot, kicked it.
The goal, he set the ball for Messi to start the attack play; his shoot was a tight angle and if he passed, it would have been blocked by Upamecano; I think everything he had done there was good.
The header was bad, he mistimed it completely, but again showed up at the right spot to do it.
He has what it takes to become a WC striker, and the contrast between him and Álvarez actually makes me understand why is he valuable more, they are both developing, but Lautaro is further up in the development stage, and IMHO Lautaro is actually a way better striker than Vlahović. I know I will get a lot of hate for this, but if Lautaro becomes clinical, you can start comparing him to Van Persie, Benzema.
All my friends are asking me how Inter scores with Lukaku and Martinez btw.