Captain America: Brave New World may have a secret villain that can bring back the best parts of Cap's mythos and Secret Invasion.
Red Hulk Explained: How He Fits Into Captain America: Brave New World
Secret Invasion introduced MCU audiences to The Harvest, which had the Skrulls walk through the battlefield where Thanos fought the Avengers in Avengers: Endgame. Their goal was to collect DNA samples from every enhanced being that had spilled blood in battle, be it Captain America, Captain Marvel, Black Order, Black Panther, or Thor.
A theory on Reddit suggests that Captain America: Brave New World may carry over some plot points from Secret Invasion, specifically how the Red Hulk was created. It is expected that the character will have a different origin story, and could conceivably be a Skrull agent, which hearkens back to the "New World Order" subtext that was scrapped.
A theory posted on Reddit by u/Former_Assistance526 suggests that the Red Hulk in the MCU could only be created from The Harvest, just like the Super Skrulls are, or indeed Thunderbolt Ross could be a Skrull himself. Not only that, but given that Red Hulk seems to be a call back to Red Skull, who was similarly obsessed with a super-soldier program, maybe only Ross or Skrull-Ross sides with a still-fierce Hydra, who could using the Serpent Society as one of its wings.
