I think you might be underestimating how much there is too the field of motion graphics. And just understanding something doesn’t mean you can do it–just like a professional movie critic probably couldn’t make a hit movie because they are two different things. Think of trying to be a clay sculpture but you never really touch much clay, but understand how it is done; you need to get dirty and going through the motion of creating, and finding what really works in all sorts of unexpected contexts. Basically it takes experience like anything else in life.
As a motion designer, you don’t just animate graphics, you can be called on to do all sorts of motion endeavors–you are often the Swiss army knife of post-production.
This is tough love, but just how you are talking about things is unrealistic. You need to put as much energy and passion as you are in your Phd (time) if you want to be a successful motion designer. If you don’t, you probably are going to create unprofessional work and have mad clients. Motion design as an industry has a moving ground–you need to keep up with all the changes occurring or you get left behind pretty quickly. That takes time into itself.
Good luck.
Best regards,
Kevin Camin