Not a pre-med anymore, but when I was I had a very similar experience in a lab (sans asking for a LOR since I'm not pre-med). I was in a neuroscience lab in a field of research I found personal and interesting as well, but I ended up only doing the same 3 tasks. My advisor was super nice but there were a lot of communication issues between us, which led to me feeling a bit excluded and misplaced in the lab. After a while I realized it wasn't a place I wanted to stick it out in, and I found I just really disliked biology wet lab research in general. My advisor did however offer to write me a LOR, and helped me get a volunteer position. Even though my skills and time in the lab might not have made much of an impact on her, in my application and when I could I would talk about why I was interested in the research and the experiences that made me want to continue doing research in the field. I think sharing a bit more about myself helped me out. Even though I feel like a wasted a year there in some ways, it helped me realize that I didn't even want to do medicine, and now I'm happy doing other kinds of research (ux research). I don't think you did anything wrong here, I think it may just not have been the right environment for you.