While I was watching Captain Marvel I got enlightenment, an answer to the question: Why did Thanos wait for collecting the infinity stones?
There are a lot of theories around the web so I’ll tell my own. Please, not that this is not a theory related to the plot but simply a narrative construction point of view.
Is obvious that the MCU is an interconnection of movies and, even if some of them are as meaningful as a fart in a wind storm, or better, they are not suitable to story itself but in order giving few seconds of hints for future movies like Ant-man and the wasp.
But, beyond this, we can assure that every movie has its own plot that is partially self-contained.
For example, there were theories and theories on how the pager will be explained.
Now. This could be very good if you see only the big picture but they are still separate movies.
We had theories about ant-man that went there while escaping the quantum realm, or the ancient that could appear in the meaning to tell fury about the future and more, much more.
The plot meaning:
And here we are for the infinity stones: If Thanos started to collect all the stones during the movies we had scenes where the only constant should be a bunch of profanities from who went to see them and rightly didn’t understood how such moment could be fit into the plot.
So what the Marvel studios did was position the stones where they should be in order to be collected from Thanos.
Furthermore, they get plenty of space to the introduction of the stones and for the superheroes to be loved and, finally, for us to wait for the big reunion.
This is not going to erase the concepts in the post about cinematic universes but is indeed reinforcing his topic.
Concluding. Is funny to see people trying to make theories about air and maybe the directors even thought on how to fit this plot need into a good project. Hope they don’t stop now.