From my understanding the job of a theoretical physicist is to derive theories to explain phenomena in nature. But let's say you aren't the best problem solver in the world. You are good enough in your physics class to get the 3.5 GPA but you are never able to solve those extra credit problems or those super hard challenge problems at the end of the exam or chapter. Well you might be able to solve some of them but it might take months or years while someone can solve them in an exam setting. Does that mean you will be a bad theorist if you can't solve the those kinds of problems?