Improving motivation in qualitative research motivation
Let me try to make two points, one about you and the other about Grounded Theory. First, though, I don't know you and so am extrapolating and I'm not involved with grounded theory other than having evaluated a thesis and a tenure decision. 

About you: Many students reach a point in their research at which they start to doubt the value of it. This happens in many fields. But one of the reasons for the doubt is that the student begins to know and understand the theory and so it starts to seem somewhat simple and maybe inconsequential. But that is a sign of growing expertise. What seemed hard at the beginning, now seems less hard and maybe more obvious, so, what's the point. This is the sort of thing you just need to power through, hopefully with the help of advisors. If the advisors are good enough, and actually involved in grounded theory, rather than just external observers of students, then you should be able to trust their advice. 

About Grounded Theory: I'd never heard the term until I was asked to serve on the tenure committee of a new faculty member. I reviewed her work and was astounded at the depth of understanding she brought. I became one of her chief advocates through her attaining a Full Professorship. Why?

I was trained in mathematics and later switched to computer science. They are similar to each other in some ways. I've written here in response to other questions about what is required to be a mathematician. It isn't just deep knowledge of mathematics, but requires insight into how a field of study works. It is one thing to be able to follow or reproduce the proof of a known theorem, but it is a completely different level task to be able to propose what might be true with enough confidence that it is worth spending time and effort evaluating the truth. It is easy to make random statements in math and easy to extend things trivially, but much harder to even conceptualize something over the horizon. 

But it is just this sort of thing that grounded theory attempts to do. It is very difficult. But, when done well, it will come up with questions worth studying. Integrating the various threads of thought what are unfocused and incomplete into something that can be rigorously studied is a big deal. The world is a messy place. Grounded theory attempts to make some sense of it. 

But, and you have pointed it out in the question, it has to be done carefully and rigorously so that you don't just put a stamp of "science" on shoddy thoughts and preconceptions. It is very difficult to look into messy data, even contradictory data, and discern the inner workings. Even to discern what might be the inner workings is very hard. You need to rigorously question every assumption as those may lead to error. But you already know this, and, I suspect, that since you recognize it, are well placed to follow through on the required rigor. 

You've chosen a hard path, actually. I wish you well along the way.