I mean, Captain America doesn't own the concept of codenames.
We don't "need" to do anything in a fictional world about super spies but I think it'd make the world more interesting, and quite neatly explains why the same man has been at various levels of his career, physical fitness, skill, knowledge, and face through the decades.
I have never heard of an actual logical reason that it shouldn't canon, and you haven't provided one either
I'm definitely not old (~30), and my preference has generally been my age +/- 5 years.
As I've gotten older, I've noticed that my sexual attraction has migrated from being solely based on physical attributes to being partially based emotional connection, intelligence, passion, etc.
I think it's also important to note that an individual's "peak attractiveness" can occur at different stages of their life.