My comment also has nothing to do with "focus" or "screentime".
It has everything to do with the storyline.
Have you seen the movie?
Actually, in thinking about this further, if you want to get technical, all things lead to Odin, not Stark. I'll elaborate...
Odin left the tesseract (space stone) on Earth, which Red Skull used to create weapons, giving Axis the advantage in the war, which resulted in motivating Erskine to counter Red Skull with a more perfect model of a super soldier, one for good, aka Steve Rogers.
Odin banished Thor, leading to Thor coming to Earth, leading to Loki taking an interest in Earth. Loki became interested in ruling because he felt it a right denied to him being the adopted and, in his eyes, considered lesser brother, of Thor.
Once again the tesseract, that Odin left on Earth, plays into Avengers 2012. Thor stated that use of the tesseract by SHIELD signaled to the universe that the Earth was ready for a 'higher form of war'. It also attracted the attention of Thanos once SHIELD started using it in much the same way that Red Skull did... aka to build weapons. Thanos gave the mind stone to Loki to use to invade Earth to retrieve the tesseract in exchange for Loki getting Earth to rule. The scepter which housed the mind stone, which ended up on left Earth after the battle of New York, resulted in Wanda, Pietro, Ultron and Vision. None of which would have happened if Odin never left the tesseract on Earth to begin with.
The Asgardians give the reality stone to the Collector on Knowhere.
Asgard protected Earth for centuries. But Odin kept a secret from both his sons. They had a sister. Loki banishes Odin, Odin dies, Hela is released, Asgard falls and there goes one of Earths protections. Roughly the same time Ego weakens Xandar with his antics during GotG 2. And the Ancient One dies. All of this makes everything really freakin' easy for Thanos.
And if the MCU is truly going to make an Eternals movie, in the comics, Odin is responsible for them, too. Thanos is the decedent of the Eternals. The Eternals came to be because the Celestials messed with the gene pool of humanity back when we were just discovering use of our opposable thumbs. The reasons the Celestials did this? Odin wanted a treaty with them, Earth was under his protection at the time, and he offered Earth up to the Celestials for experimentation to get that treaty. The Eternals were the result of that experimentation. They are immortal (thus the 'you should have aimed for my head' line). Thousands of years ago they had a civil war, the losers were banished from earth and settled on Titan.
So, really, if you want to get technical the MCU is not Stark's story but rather the result of Odin.