Public universities are much less forgiving, which means mediocre or unmotivated students get crushed in cases they would get hand-holding (and A- grades) at a private university.
As for connections, they're important and you get better ones at top schools, unequivocally, but you don't need them for many careers.
I went to a public school for CS. Noticed same. First and second years are full of "filter" courses. Calculus, Physics, and CS 101 weeded out whole swathes of students. Many large classes where you are mostly a faceless StudentID #. Many students switched majors, some schools, some droped out. It was brutal and this wasn't even a top tier school.
After that it was a lot better.
I'm not advocating hand holding or coddling, but I do think that impacted majors at very strong public universities aren't really doing right by the talent level they enroll. They do society no favors by enrolling a student who didn't have a strong high school calculus curriculum, giving her a C her first semester, and then telling her that her GPA is too low for engineering now.
My own grades are highly erratic - I dominated in some of the hardest math classes where I went to undergrad (a public school), often being one of the top performers and easily the most knowledgeable, but did awful in other classes. I never cared that much about easy classes, and only applied myself on hard classes because they were mentally stimulating/challenged me. I also did not care about grades - I viewed my purpose at college to learn & develop, not be a 4.0 student.
When I went to grad school (a prestigious public school), I applied myself in all of my classes and did solid overall - all of my classes challenged me pretty hard, and so it motivated me to work hard.