Captain Americas iconic look is in his full costume with his shield, he's almost never in his full costume and he's ditched the shield (though I hope he'll get it back in Infinity War).
Thors iconic looks is in his full costume with Mjolnir, it took us until Ragnarok to get him in the iconic Thor helm and Mjolnir has been blown up now. Though I will agree Thors hair was pretty iconic, but to say that they've done it just so Chris Hemsworth doesn't have to wear a wig is just completely retarded.
Black Widows iconic look is red hair and the black cat suit, which is great and all, except that she's supposed to be a superspy, so she needs to change her look.
The looks are changing and evolving as the characters do.
Once again, you are looking for criticisms at this point.
You've mentioned "Brand" numerous times. The Brand for Cap is his shield (that's gone), the Brand for Thor is Mjolnir (that's gone).
Let me tell you the only "Brand" anyone who watches these films cares about: