After 24 years at the university, I can say, "Yes, they are good." Note that I left it at good and did not say they are great or the only.
In many of the cases where I have had to deal with students making poor grades, there were low test scores in their records. But, I have had many poor students who had higher scores. They were not applying themselves or had taken on too many responsibilities. In fact, I often tell students, "There are three activities in life: Full-time school, Work, and Family. Choose any Two. (Because one cannot do a good job in all three--one or more activity will suffer poor quality.)"
Motivation is probably the best predictor of college success.
My son struggled in college (after obtaining rather poor ACT scores) and left after 3 semesters. He went to welding school, worked in a warehouse, and has been in a welding job for about 1 year. On a recent trip to an equipment manufacturer sales office, he instructed them on how to do something with their machine they did not know how to do. He also received a verbal solicitation for employment from them. On his job, he has gone from welding only to reading prints and setting up jobs. He also amazed them in understanding computers and spreadsheets when the person responsible for the tool-crib inventory was out sick and someone else needed the information.
If I sound like a proud papa, I am. Success in life is more than initials behind your name. I think both of my kids are on their way toward those successes (each without college degrees). Don't get me wrong - degrees are important for many people (myself included), but there are other more important things: being satisfied in a job, raising a good family, being honest, etc. - all the things you teach.