We spent some time discussing the absurdity of and plot holes within this movie. The story completely falls apart upon inspection and tail spins downward very quickly.
As it became a bummer discussion topic, I concluded that we would have a lot more fun using the movie's information to determine ways the Avengers might defeat Thanos.
My simple approach -
Have Ant Man go quantum realm, enter Thanos' head, then re-expand to full size. This would explode Thanos' head and kill him.
Also suggested -
The Avengers should then grab the Time Stone (green) and go back in time and kill him before he had the Gauntlet.
Nagging Questions -
If you have the Space, Time and Power Stones you do not need any other Stones. You can go anywhere, at any time and do any thing.
What is the difference between the Mind Stone and the Reality Stone?
What is the Soul Stone and why doesn't it feature prominently or ever get used at all?
OUR CONCLUSIONS -
These movies are made for 10 year old boys. Adult mind sets need not apply.