Fringe Theory Here:
Infinity War claimed to be the "most ambitious crossover in history", this got a lot of flak. But what if this was actually true? I personally believe that this is actually a huge cosmere story in disguise. What if each of the characters and their powers are actually using forms of Investiture? Their backstories have just been huge cover-ups for when Marvel reveals that Brandon has been writing the movies all along.
The Infinity Gauntlet is actually a massively powerful fabrial. Each of the stones is a perfectly cut gemstone that most likely holds some form of godspren.
Iron Man's suit's amazing ability to shape itself into whatever he wanted was waved away with the word "nanobots". However it makes a lot more sense that it is actually a form of Shardplate. Although we don't exactly know how Plate works, its quite likely that it could take the form of Iron Man armor. Tony Stark's flight can be attributed to the Surge of Gravitation. It makes no sense that a heavy suit of armor could fly under its own power solely relying on the little blaster things, so the idea that he is using lashings clears that up. The Shardplate is clearly augmented someway however, in order for it to shoot missiles and provide communications. Perhaps it is a blend of modern tech and Plate. In addition, the laser bursts he shoots could be simply something added onto the Plate, but since we are already assuming Stark has access to Gravitation, it is far more likely that the blasts are simply a blast of the Surge of Division. This would put Stark as a Skybreaker of at least the Fourth Ideal. This fits well with the fact that he was willing to bind the Avengers to the laws of the United Nations.
The Hulk is some form of Hemalurgic Construct very similar to Koloss. His spikes allow him to Compound pewter, giving him crazy amounts of physical strength. I'm not sure where the spikes were placed in order to allow him to control his transformation. There is so little that we know about Hemalurgy and constructs that this is extremely plausible, especially because of the fact that Koloss turn blue.
Thor's hammer and later his axe thing is a type 4 biochromatic entity. These extremely Invested objects have been given commands that allow only Thor to wield them.
Captain America and a lot of other heroes are twinborn using Allomantic Pewter and Feruchemical Gold, allowing them to be stronger and heal faster.
Rocket Racoon is a Kandra, not much more to say on this.
Spider-Man is an extreme form of an Awakening Savant. He has created a type of extremely strong and lightweight string that he gives a command such as "Grab Things" I'm not sure which heightening he is at, but he clearly has a lot of power and skill in order to swing from line to line so effortlessly.
Doctor Strange is using a magic system currently unseen in the cosmere, although it has numerous similarities to AonDor.
In conclusion it is highly probable that all of the Marvel Heroes are using some form of shardic Investiture, I have no doubt that at some point it will be revealed that the MCU is part of the cosmere. Any holes or missing explanations in this theory will likely be explained in later cosmere novels.