No, but it would help when you go up for Tenure! Seriously, you do not have to be an Einstein in absolute terms, but the catch is that as viewed by non-scientists, you DO have to APPEAR to be as brilliant! As for any career, your skill and competency are determined by how much raw information you have been able to accumulate under your skull, and the skill that you have in manipulating this knowledge. In astronomy, you have a vast body of basic facts that you simply have to be fully competent with. Along with that, there are an equally vast array of tools you must have at your finger tips which let you figure out the physics of what you are observing.
This latter resource can only be acquired via the textbook and lab approach as an undergraduate and a graduate student. Sadly, there are LOTS of people out there in the world that think that they can short circuit this learning process and get right into crafting theories of the universe. They are wasting their time, just as they would be if, after reading one page of the business section of a newspaper, they though they could go out and run a bank or plot the economic future of an entire country. Good intentions and enthusiasm are simply not enough currency to become a competent, professional astronomer with a shot at a long-term career in this business.
So, you do not have to be an Einstein, but you do have to be amazingly competent and knowledgeable about how the physical world works. In as much as some people think that our educational system is 'broken' because it stresses rote learning in the early years, this is a process that favors the sciences because for much of your early years you have to simply absorb lots of facts about the world. Creativity comes later after you have filled your mind with basic information. Educators don't like this approach these days ( called Drill and Practice) because they now want everyone to go into a classroom and act creative. But you cannot be creative in an intellectual vacuum devoid of a basic set of facts about the world.
Oh well, I digress!