'Useful' toward what end? Beware that thinking related to "personal opportunities to climb the ladder" is going to be shaped, probably a little too much, in this forum by the technologies and economic forces now producing what passes for wealth and happiness. The current thinking is that the world and the future belong to the young, that young thinkers, leaders and workers have the greatest impact, and that any misstep causing a loss of speed coming out of the chute will predictably lower the path of life's trajectory, which inevitably peaks around age 35. Within that world view, one must learn as much as one can as fast and as early as one can, and personalized full-time education face-to-face with skilled teachers is a great advantage as long as it does not last too long.
Another perspective to consider accepts that one has a time to be young, and with some probability our paths traverse times to be mature, middle-aged, old, older, and superannuated. With this in mind, the argument for optimizing the entire path is strong. Find a way to do that, and you will be called wise.
Your question does not mention age and does not say that you are young. I should not assume that. Lack of lifelong learning is an alleged driver of the hideously extensive withdrawal from productive work now seen in persons who have reached age 40 or more. Unfortunately, widely available and affordable full-time education face-to-face with skilled teachers for persons of any age is not a feature of the current educational landscape that I know, so lifelong learning cannot proliferate unless it contains a considerable dose of self-education.
Consider that much of education, regardless of context, is self-education. Almost everyone learns almost everything best by doing it, and sadly, learns it fastest from their own mistakes. The greatest value of skilled teachers may be that they illuminate the learners' blind spots, but skilled peers can also do the same. Of course, learning styles, psychology, background, culture and personality determine who can learn what from whom, but a mixture of teacher-led and self-driven education may be best.
If education is a process sustained by society so that its citizens know what the good life is and are capable of making good lives possible with the goal that the citizens will actually live good lives, the proper time to evaluate our educations is when those lives reach completion. This means that now we should be considering the lives of those educated back in the 1940's and 1950's and evaluating the benefits and deficiencies of those educations accordingly. Similarly, a young person choosing a course of education today should at least spend a little time trying to think ahead to 2080 and project what they will then be glad they learned in 2018 and what they will wish they had learned in 2018.
The practical wisdom used to be, "To play billiards competently is a sign of a good education. To play billiards too well is a sign of a squandered education." Good luck.