The Chitauri are faceless mooks, not someone who personally attacked those close to him and forced him to watch. Thanos made it personal to Thor, that's why he did it. It's an entirely different situation and comparing them doesn't make any sense unless you just have no understanding of the character at all.
Apparently, you move the facts aside when convenient. By the time of the first Avengers movie, Thor had an established emotional investment in earth--in fact, his close friend Erik Selvig was right in the middle of the chaos, with Thor knowing his life was in danger, so to end the conflict as quickly as possible (thus increasing the hope that Selvig might survive), he did not employ a halfass / clueless tactic that left his enemies alive. The same applies to Thanos--only the threat was greater, and he fully understood that, so there's no excuse for this poor set up for a 4th Avengers film, when every other character around him (Wakanda) were trying to kill Thanos out of the gates. They all had everything to lose, and faced Thanos with that in mind, yet Thor just drops the ball at the most crucial point.
If he's angry due to Thanos killing Loki (and he was), and knew what Thanos was attempting, then he should have been more motivated to deliver the death blow, instead of only going far enough to allow a undeniably desperate creature enough of his fading energy to use the very thing Thor was trying to stop.
All things considered--character motivation, the do or die stakes in preventing Thanos from getting every stone, there's no sense in the writing a character who consciously comes up short when it mattered most.