Linguistic drift is not a directed process, and that something seems sexist is the result of you (that is, the observer) ascribing intent to this process. I could say that yes, it's really horrible how men lost their unique identity, and are now just considered the unspecified rest of humanity, but that is probably not the way most consider "man as the default" sexist. I would beg you not to assume malice where there is none, and ask you instead how quickly you would grow tired of adding another syllable to the otherwise completely unambiguous word "man".
If I went to Germany, after brushing the dust off of my German, and called a young, feminist woman "Fraulein", the equivalent to Miss and Ma'am, as I was taught in school as the polite way to address a woman of uncertain civilian status, she might very well have a conniption fit because "-lein" happens to be a diminutive suffix. If I called an older, unmarried woman, grown up before this last wave of feminism, "Frau" instead of "Fraulein", she might very well be insulted by my assumption that she, as a woman past her prime, must be married, and inform me that it's "Fraulein" oder das Autobahn.
In this example, different points of view in two different persons will lead to both available options being sexist in one way or the other. I could be accused of sexism merely because some people think that they can project their opinion and experience upon others, because if they used the language like so, it would be as a deliberate insult.
In the end, language is far too complicated to be reworked every time some potentially problematic words are brought into the light, and should instead be accepted as a system built upon relics of the past, where changes should serve the interests of practicality, decreasing ambiguity and increasing ease of use. The surname conventions of Krypton could very well be a result of sexism in recent time, or it might be a relic of a hodgepodge of ancient inheritance laws being misread by a gaggle of hipster scholars, who thought they should use it because it was really retro.
An important rule of forensic anthropology is to never project your own values, beliefs or convictions upon those you study.
