Can bad students be good scientists?
I think most would probably agree that there are cases where someone is a poor student but has the potential to be a good scientists -- because what defines a good/poor student is mostly the ability to be effective in exams (i.e., most importantly to be able to learn and reproduce known material) whereas the skills necessary to be a good scientist are different.

That said, it is clearly the case that the two skill sets are highly correlated. There is a perception in the public eye that the best scientists are mavericks who are able to think outside the box and swim against the scientific consensus to find the things that nobody else sees. But in reality, that is probably a glorification and even those rare insights like quantum theory or the theory of relativity can only be found by those with profound and deep understanding of the existing knowledge, and the ability to synthesize knowledge into something new that those who have not paid the same level of attention to the details of the field can not.

As a consequence, what I read from your description in the question is that you may have the skills to be a good scientist, but that you lack the knowledge and maybe diligence to compete with your peers. That's not your fault, of course, but it's an insight that you may want to keep in mind when thinking about your future. Knowledge is, after all, something that you can catch up with if, for example,you are willing to take some time off from other responsibilities and focus on learning the basics at a more profound level than you had the opportunity to do in the past.