I think most people should start with 1.e4 e5. You should first Get a good grasp on what a center is and how to play with it before learning other fancy openings to play around the center
why is e5 more popular than c5 at lower levels of play?
Yes Bologans book is Around 500 pages but its two repertoires in one. One is simple and easy to learn the other is sharp. He also covers multiple lines for black inside the repertoires so its not that bad. He also have a section explaining general themes in 1.e4 e5 openings the book is a good one
Yes, I plan to get Bologan's book at some point, it looks really great. But there are a lot of paths that white can force you down that you need to be ready for, and not all of them can be handled on general principles. Die Schanze is right: you have to learn the basics (and in some cases, some critical lines).
But this is why I love the open games, because I think (at my level, at least) open games are key to improvement in active piece play, king safety, and overall tactical experience.
I do think this is somewhat less true about the Sicilian. White can respond to the sicilian in a variety of ways too, but white has more options to keep the position closed, and thus the chess less sharp. And I think the sharper the better for learning at sub-expert levels. (Others may disagree with me on this, but my own experience leads me to this conclusion.)
I think the question should be why 1... e5 is popular at beginners and grandmaster level, but not in the wide range between 1000 and 2500.
My own experience was that white has many lines against 1...e5, which are very dangerous against unaware players. So black has to learn some basics or he runs away into some opening the where the white player is the unaware one. Some players have tried every rather correct try against 1. e4, some of them maybe more then one time. They waste much more time in learning new lines before every tournament then they would have needed to learn 1...e5 and keeping it up to date.