Despite having to do all of this preparation, the brutal truth is that once you start on the research, there is a good chance things won’t proceed as expected. It’s possible that few of the milestones will be met, and some of the projected outcomes might not be achieved. If experiments go wrong, you might not have time to do all of the public-engagement activities you added to the grant application. Nevertheless, when the project is finished, you might well have managed to produce great science, although this could easily differ from that outlined in your original proposal. And that’s OK.
Panel members tasked with deciding who gets a grant also find the process cumbersome. I’ve been on panels myself, and sometimes there just isn’t time to read everything. As a panel member, you are usually asked to focus on three main questions. Does this proposal fit the call brief? Is the proposed science good and novel? And are the candidates experts in the right field? The abstract and a small part of the research proposal answer the first two questions, and, when it comes to the third, I prefer to use Google to learn more about the candidates.