Throughout my PhD I learned that there are lots of stumbling blocks that prevented me from getting to my goal of solving some problem. One of them is that some of the things I needed to learn were inaccessible and posed a number of undesirable difficulties. For example, sometimes papers I need to refer to are written in a language I don't understand. Some books lack notation indices, with the result that the book was difficult to follow. Sometimes the papers are hard for non-experts to understand, and I would waste a lot of time wondering what an author might mean. Sometimes nobody at my university knew the answers to my questions, even though they are on "well-known" facts (well-known to the experts but not to the non-experts). Sometimes I would be given incorrect information from an expert. In many of these cases, I didn't get my questions answered until some expository books on the subject came out. In other words, a great deal of inefficiency can arise that cause unnecessary and unhelpful delays in establishing a publishable result. I think these difficulties are causing delays in my own research. Keeping everything else the same, another researcher who doesn't have to encounter all these blocks would arrive at results faster and would publish more papers, and would be seen as more "exceptional."
How do researchers deal with these issues? For example, how do they learn some material that is hard to learn from reading the literature and books?