I would tend to agree with most of what you said, but i do feel like that how you feel about "normal" and what you consider is IMO.. how should i say this.. up for debate? Thats probably the best i can come up with, due to my, limited English Vocabulary.
But before i go any further on why i think certains things you wrote are probably not correct. We have to set some lines here, because i dont feel like we have them yet. Where does Incest end in this debate? Incest surely isnt just Mother/Son Father/Daughter Brother/Sister and/or Father/Son Mother/Daughter Brother/Brother Sister/Sister. There are Aunts and Uncles,Nieces and nephews, Cousins and so on.
Anyway, if we take a look back at Human history, it becomes very clear that Incest was pretty "normal". In Egypt it was common to marry a Sibling even amongst the common folks not just amongst the High priests and Pharaohs. Even later among the Greeks it was still accepted, Greek God Zeus (the King of Gods) married his Sibling Hera. Now just as a side note, neither the Egypts nor the Greeks favored Incest between Parent/Child, but between siblings it was just fine (I honestly dont know why).
However even if we now skipp like a thousand years or more right into European Aristocracy and follow those up unil the 20th Century. It was still very common to marry a cousin.
And if we now for a moment think about what life was like 100 years ago for common folks around the World. Back then your World was very small, sure people in Cities had more Choice, no one argues about that. However since im Interested in History and i worked in an Retirement Home for a few years i talked to my fair share of old people who were alive at the time, and not the Majority of people lived in cities, i'd even go so far as to say its not even the case Today, but i didnt research that so thats just a guess. Now your World is the Village you are in and the one thats closest. That is from what i've been told pretty realistic, sure on some occations you met other people outside that Bubble,but your day to day life was basicallly that. And i've met a lot of people who married their first grade cousin, and most of them by free will. Not because the Parents told them to.
Now if we look at that, i can say that Incest even if it didnt include Parent/Children Incest was at some point in time actuallly "normal", even in recent years. And sure in the Western World duue to a Flight being cheaper than an Uber and Internet and Smartphones and what not. People have Long-distance Relationships, change places for work meet a partner hundrets of kilometers away from where they come from and so on. There Incest isnt really that common anymore, but there is a big portion of Humans who dont live in the Western World. Sure they have internet and Cars and what not, but for them the Bubble is still very small, compared to what we in the Western World think our Bubble is (When it is in fact an Illusion, no one really knows yet how to Handle Social Media etc. , its a big experiment and we will see what comes out at some point i guess). There you have more or less the same Situation we all had up until i dont know lets say 60-80 years ago. What we see as "Normal" nowadays is very subjective, and very new. Incest was for like 99% of Humand History "normal" "common" "fine" whatever you wanna call it. Its just that in the last Century the Western World decided that it should be Taboo. I didnt really research why, but my guess would be that we figured out it has a huge potential for the Kids to have Health Issues.
Now do i say that Incest is still common nowadays? I think actual Parent/Child Incest is uncommon in the Western World (and im excluding Incest caused by Rape, because even tho thats a whole other Story whether that was/is common. IMO Rape is one of the worst things a Human can do to another, and therefore it should never be seen as "normal" and therefore disqualifies for my statistic, period). Same goes for Incest amongst Siblings, i agree with you when you say you dont buy the "IF i had a Sister that Hot". I have yet to meet a Man who isnt blown away by my sisters beauty. And while i can certainly see that she is in fact gorgeous, thats where it ends for me. Even in my Teens where you literally get a boner when a warm wind blows into your pants, i saw my Sister naked almost on a daily basis in our shared bathroom. And not once was i aroused.
But Incest amongst 1st and 2nd grade Cousins? Oh hell yes do i think that is common, maybe not that much anymore in the Western World, but even there in the more rural Areas, i still think it happens more often than we think.
Edit: Just wanted to add, if you can be bothered at some point, look up how many Countries in the World have actually no rules against Incest. That might give you the right picture of how common Incest in any form might actually be around the World. And just we who have rules against it, actually talk about it because we were told its taboo and therefore make a big deal out of it.
