A recent Slate articles warns that coffee makes you less productive. The main claim is that coffee has no cognition enhancement ability but, instead, a range of negative side-effects. Unfortunately, it is not backed by serious research.
There is much we do not know yet about coffee. However, on the whole, the research is clearly positive. Here are a few quotes from research papers:
Aged rats supplemented with a 0.55 % coffee diet, equivalent to ten cups of coffee, performed better in psychomotor testing (rotarod) and in a working memory task (Morris water maze) compared to aged rats fed a control diet. (Shukitt-Hale et al., 2013)
The results demonstrated that consuming caffeine significantly reduced the number of errors and time spent for tracing the star, and also the MMSE [cognitive test] score was significantly higher (…) (Nadji and Baniasad, 2011)
Coffee is associated with a reduction in the incidence of diabetes and liver disease. Protection seems to exist also for Parkinson’s disease among the neurological disorders, while its potential as an osteoporosis risk factor is under debate. Its effect on cancer risk depends on the tissue concerned, although it appears to favor risk reduction. Coffee consumption seems to reduce mortality. (Cano-Marquina et al., 2013)
If your intellectual productivity is low, stopping coffee is almost surely not going to help.