(MA Cantab matriculated 1997)
> kids more passionate about drinking and clubbing and gossiping than studying ... not like the world of Turing or Feynman at all.
I think you may have underestimated how much Feynman was a prankster, womaniser and bongo-player who occasionally did some physics as well :)
> you see them in the lectures, then you go back to your college
There's kind of a hidden initiative test here; it doesn't have to be that way, you can organise alternatives, and there's a whole intercollegiate infrastructure of extracurricular activities. There was a somewhat long-running university computer society when I was an undergrad, through which I found all the hackers, and some of us ended up starting a hosting service in my third year: https://www.srcf.net/ - that taught me far more of practical use than half the computing course.
May balls: yes, these are a bit odd and above my personal poshness threshold. I think they really do date from the era of Turing but not his subculture within that era, the big black tie social event belongs more to capital-S Society of debutantes and aristocrats.
> What I found shocking is that so many students were doing poorly academically.
The difficulty gap is real. Unlike all the education system people will have encountered previously, you can't coast unless you are very smart, and there will be extremely challenging material. It's .. deliberate is the wrong word, but there are certainly tutors who will up the difficulty level if their students are not struggling.
The mental health and motivational/pedagogical thinking is also stuck in the 19th century. Some of this does need to adapt to today's students.
> The more ambitious kids were more busy padding their CV to land a good job than doing what interests them.
This is far more what Oxford is "for" in British society because that's how you get ahead, unfortunately.