What you're describing isn't graphic design, exactly. A job where you throw out ideas and then leave, and are done with the project, would be consulting or creative directing. The thing is, the people who do those jobs have spent years working through the ranks, putting in their time, doing the actual work that would bring those ideas to fruition. And/or, they're brilliant and highly educated (think masters degree.) In short, it's not an entry-level position. It comes after lots of hard work, lots of years on the job, and as a result of a cumulative portfolio and reputation.
If you were to pursue a degree in graphic design, your classes would cover the elements and principles of design, color theory, typography, and advanced industry-standard software programs, for starters. In most schools you'll also take (and be required to pass) foundational art classes and art history classes. Often graphic designers are also proficient illustrators, computer programmers, or web developers; skills which make them more versatile to potential employers.
The field of graphic design is highly competitive. There's a lot of designers out there, and many of them have insanely expensive degrees from art schools. And, since it's a job that can be done remotely, freelancers in North America and Europe are competing with people in emerging markets like India and China, where designers are able to charge much less for their work due to differences in the cost of living.
I don't mean to totally rain on your parade, but I'd rather your decision on what to study be as informed as possible. School is expensive, and you don't want to find out part-way in that you don't actually want to do for a living what you're studying.
That said, there are definitely careers in 3D animation. Depending on the school, it may be its own program, or it may be part of an illustration program, or something else. A career counsellors will be able to guide you in that regard. If that's what you love doing, then definitely go for it! But be prepared for the reality that you're most likely going to have to do the grunt-work for a while before you advance to directing or consulting.