1. If one is independently wealthy, and can afford to learn full time, college is clearly an extra. For most of us, that isn’t an option. If you can manage a job working as a teacher (or similar occupation) within the frum community, that is another option (albeit not a financially rewarding one).
2. All secular work involves bitual Torah. College plays the same role as a traditional apprenticeship. In some career you start at the bottom and work your way up. In others one needs to go to college first.
3. If one feels unable to associate with non-Jews but still wants a career that requires a college degree, distance education degrees exist and some of quite reputatble (e.g. Maryland’s University College, New York’s Empire State College, etc.).