Let me try to address some of the issues you have raised.
Every society in the world has rites of passage for it's young. In the West, these tend to follow the education calenders. Thus every American high school graduate will attend a prom dance WITH A PARTNER. Jews have their bar mitzvahs. Etc.
Rites of passage do not mean that life will end if they are not marked. They are not a matter of life and death but more about communal cohesion and order.
That's why in fact other rites of passage such as weddings and even funerals are held. They mark the end of one stage of life to the next. Surely @Aviator
, you would still be able to sire children with your wife even if you didn't have a wedding? Why then did you hold the expensive event? To tell the world that you and her had gone to the next level, that's what.
, who has still not sent me booze, said, the Gikuyu rite of circumcision was meant to be more that the mutilation of the penis. Remember back then there was no pornhub, for example, and the young still had to be taught about sex and sexuality. Or about their responsibilities as young adults. This happened during or after circumcision.
I notice you take exception to the choice of the maternal uncle as a key participant in the irua. Surely, surely my brother you are better than this.
The maternal uncle was taken to be a safeguard of his sister and her children. If for example they were chased from their matrimonial home, it was the uncle who would show them where to stay until the woman remarried. He would even be expected to give up part of his land for this.
For this and many reasons, the maternal uncle was held in great regard. You surely know the saying "mama gwithua mukonyo"?
Of course, looking at many of these things today, some may not make much practical sense. But as long as they do no harm, like eating turkey during Thanksgiving, I don't see why we should not uphold them.
I for one will not ditch irua to go embrace stupid beberu traditions like Valentine's and Halloween. I will take my mpango kids, Kiiyo and K Jr to the elders for the cut after they have sought permission from their uncle. I will build them Simbas and tell they are no longer boys.
And I'll tell them to be proud of their great Gikuyu culture and history of their people.
Then I'll warn them that if they ever bring a boy home eti sijui nini nini, I'll shoot them dead and then hand myself to the police.
Ni hayo tuu kwa Sasa.