Excellent advice and motivation to the questioner. Study the correct materials, learn those principles of development and then play, play, play. Old skills will eventually be replaced as you develop new ones. I played in world class table tennis tournaments because I learned NEW SKILLS. I still have the skills I taught myself by trial and error, but it was the new skills that were taught to me that improved by ability to become a Class A and eventually International Class player. Keep learning new principles in theory (not just a few moves) and eventually you will be able to recognize the "truth of most situations" as Kasparov states. It does require thousands of hours of truth seeking in chess situations. Forcing your opponent to make fewer choices gives you great confidence and lots of wins!
Why am I improving so slowly?
Well I can say that you have played quite a few games. I thing I would agree on is to focus more on your games instead of the rating you have. Focus on making the best move, which it seems you do. Maybe you could review opening theory or middle and end games tactics.
Do not give up on chess, each person progresses at a different level. Keep at it you will improve.
What you need to do is learn 1 or 2 openings first. After that? TACTICS, TACTICS, TACTICS. Forget about opening theory. Read lots and lots of puzzles. Go to Chessgames.com and solve the puzzle there EVERY DAY, regardless of difficulty as well as the ones on this site. You will see a marked improvement.
fncll> [W]ill that memorization help me in my games? In general, I doubt it.
Memorizing common patterns certainly does help during games, although I agree that one should know how to calculate them. Either ability in and of itself is not so strong as the two abilities combined. This position is from a game I played last week:
If you get yourself taught by a good chess teacher,it may help.