[tygorius]

The "purpose" of the opening is to get yourself into the sort of middlegame position you like to play. (Some players love having white against a French Defense, for example, while other are quite comfortable with black's side of it.) Understanding which types of positions you prefer takes experience, and while you're gaining that experience at the lower levels tactical skill can dominate. So it can seem like knowing the "book" moves for a bunch of openings is important when in fact the problem is that your opponent has better tactical skills than you or perhaps you have trouble judging a position and developing a plan. That's why specializing in a few openings can be helpful -- you get lots of practice with similar middlegame positions at the same time you limit the number of lines you have to deal with.

Now if you like open games such as the King's or Evans Gambits (i.e., fashions of 100+ years ago) things will get tactically bloody pretty quickly and so gaining a knowledge of where the booby traps are will be prudent. But if your taste runs to semi-open games, say, you can limit your opening study to a relatively small number. I happen to like the Dutch Stonewall formation as black for example, and the precise move order for getting into a position I'm comfortable with doesn't require a lot of memorization.

Happily we live in a time when computers can not only entertain us in chess but also help us with learning chess. You can improve your tactical skills by studying a tactical positions card deck in Anki for example. Or you can work on a particular opening by setting the computer to always start games from a particular position. You can use that same starting position trick to train yourself in endgame play. The important thing is to find ways to keep the game fun while you improve your play.