Most people are pretty average and plenty of average people make it through a typical Bachelors program just fine.

While there may be some concepts that some will struggle with or unable to handle, the VAST majority of school comes down to the effort an individual puts in. You won't pass with zero effort. Some may be able to skate by with less effort because they can reason better, but in the end it will always come down to effort put in.

If you are not high IQ, that means you need to put more effort if you want to get "straight A's"... it is emphatically not an excuse to give up, not try or lower standards. I say this as someone somewhat high IQ who was a bit lazy and easily distracted in school. There were lots of kids that weren't as smart that got high grades and did well.. because they put in the work. I'm also a bit older than a lot of people here (early 50's).