Welcome to Steemit @mrnoone, nice to see you here!

You're right, but that's the point. Most people haven't read the comics at all and don't know the stories at all, i.e. you have to lead the non-hardcore fans who don't know the comics to the heroes and their stories first. Because you can't flood the normal audience with informations. That's why a middle way is very important.

For example and how you mentioned it, Thanos is defeated quite differently in the comics than in the movie. In the comics there are also many other heroes involved than in the movie. The intention of Thanos to wipe out half the universe is also very different in the comics than in the movie.

You have the same thing with the story of the Guardians of the Galaxy. In the comics the different characters come and go, but you can't really make that happen in the movies without confusing the audience too much.

I think with the Infinity Saga (the movies) Marvel has taken a good way to expand the universe further, in which the powerful cosmic characters could also appear. If they had been introduced at the beginning, the viewers would have had too much trouble getting along with them.

I think that Kevin Feige did a good job here by trying to find a good middle way. Of course there are a lot of aspects missing from the comics, but we hardcore fans have to live with that.