So you like the mantle because of what the person under the suit does.
But surely you see the storytelling potential for having another character who does things differently in that suit, and how they measure up against the original and how they approach a reputation that precedes them?
Thats nothing new for marvel, they've explored this countless times because of that very notion. The mantle is bigger than the person, but the persons who wear that mantle are just people. Even Steve. So what does it look like when someone else wields the shield? Caotain america is a symbol that represents a nation. Steve rogers is a man. A man can't own a symbol anymore than one person can represent an entire corporation, or even an entire nation.
Thats the way marvel has always looked at it. They've done interesting stories with this. How does a new person wield the spirit of vengeance? What does it look like if Steve ISNT the one wearing the shield but rather its John Walker? How does he change what that symbol represents? Its no different here.
These mantles are the personification of ideas, and ideas aren't owned, they are employed, tested, exercised within people. This goes for DC guys too and why they've done the same thing. Batman is an idea. Bruce founded it, but many can espouse that idea. It can still be defined by what the originator stood for, or it can be a referendum on it. Like all ideas, it can be interpreted different ways.
These are dynamic characters, far more dynamic than simply a costume and a catchy name. They represent people and ideas, and limiting them to just the one they were created with is a missed opportunity, every single time. So I'll always be interested in legacy characters and passing of mantles . I want to see what a black spider man looks like, or does. I want to see what a woman does in the daredevil suit, how she approaches that concept. It keeps things interesting and often can make you appreciate the originator, and their approach, even more.