Homelander does not "borrow" from Superman, he is a commentary on Superman and The Seven are an analog of The Justice League (originally founded by seven heroes).
Thor, Ant-Man, Wasp, Iron Man, and The Hulk are the original members of the Avengers--created by Marvel because they'd seen how popular The Justice League were and wanted a team. Not a single one of them is an analog of a DC character and to this day The Avengers remains a popular comic book team. So, you do not need to get arbitrarily close to established characters to make a point. That is to say, name, power similarity, and character details can be quite different and still tell stories about being heroes, their problems, their relation to society, etc.
Is there a reason to get so close you have to ask the question how close is acceptable?