You are probably right that not a lot of people in the GA knew who Thanos was when he popped up on the screen after the Avengers. However, I think there are going to be a lot of "Aha!" moments when he appears in future movies.
Anyway, back on topic. I think DC needs to start building up Darkseid as the main villain as soon as they can. Let the allegations of
"Copycatting" be damned.