Originally Posted by cherokeesam
^This. Skull didn't prove to be a particularly popular cinematic villain, and the actor publicly ridiculed the role and wants no part of it. Despite comic-book canon showing Red Skull returning to remain Cap's nemesis in the present day, I don't think that particular route is very high on Marvel Studios' agenda at all.
Although the RS wasn't developed that well, he is still the second most popular MCU villain.
Source: polls, conversations, him and loki are always remembered.