The Cleveland Browns are well-known for being possibly the most incompetent team in the NFL. For superhero teams, the Avengers' incompetence is the closest to the Cleveland Browns' incompetence.
1st movie - The Avengers face a bunch of aliens who have no superpowers at all. All it takes is 1 nuclear missile to defeat the entire alien army. So all the Avengers had to do was fly into space and destroy the alien mother ship before the aliens make it to Earth. Then there would be no battle and no human casualties at all.
But instead of flying into space and destroying the alien mother ship before the aliens make it to Earth, the Avengers just stand around doing nothing but cracking jokes and 1-liners while the aliens arrive on Earth. Thousands of human casualties that shouldn't have happened if the Avengers had just been more competent and flown into space and destroyed the alien mother ship before the aliens made it to Earth.
Actually, Captain America did play traffic cop, telling people where to run to. Manhattan has been the target of several terrorist attacks in the past so the NYPD has probably trained all of their officers how to evacuate people in case of a terrorist attack. But Captain America loves being a tyrant so much that he felt he should take over the job of the NYPD officers and tell people where to run to. Being a traffic cop was sure a great use of that super-PED serum!
2nd movie - The Avengers are even more incompetent. The Avengers create Ultron. Then Iron Man and Hulk destroy a city in Africa and kill hundreds of civilians.
3rd movie - The Avengers reach a new level of incompetence by letting Thanos kill more than half the universe.
Nick Fury said that he formed the Avengers so they could fight the battles that normal humans couldn't. Well, in the 1st movie, the Avengers couldn't defeat the aliens without a nuclear missile that they hijacked from normal humans and their latest movie, the Avengers let Thanos kill more than half the universe. So why the fuck were the Avengers even formed when they're too incompetent to get the job done?