[giantg2]

"A lot of classes in CS require group work"

My general experience is that a lot of the time you will get people who suck or just don't care as part of your group.

"half the groups don't know how to code (mostly webapps),"

To be fair, the point is to be learning how to do that. Maybe there's a problem with the curriculum in your school where these individuals haven't had any guided instruction.

"for my final summer I have an internship at Google."

I'm sort of guessing, but maybe you are also a well above the skill average for the class.

So in summary, likely a bit of both - some people who actually suck, and that Mayne you are on a different level.