It depends on the model, some universities are easy to get in but have weed-out classes, some are hard to get in but comparatively easy to finish, and some are both hard to get in and hard to finish.

Discrete maths back in my days was one of those almost universal weed-out classes which got rid of people with limited abstract thinking ability who weren't willing or able to get over that with hard work. Very heavy correlation between how well you did in that class and core CS subjects.

In my EU country, lots of first year students are kind of lost and are picking their major more or less at random (or very unprepared). Very low passing rates in first year are very common. It gets better in 3rd year and after.