A super computer is supposed to be the fastest, best at everything. Right?
You are not like this. People are taught as a general population being labeled good at music means playing every single instrument in the rock band and/or orchestra, singing, piano and possibly any ancient harischord found in the oldest known caveman drawing.
I am not by any means a fan of the "Jack of all trades, master of none" theory. Yuck. Indeed, the phrase rubs on me like a mothball smell. You can be a master of multiple instruments and musical crafts. What you must know is, you should not be expected to be great at everything, and you can be Elvis to Andrea Bocelli, John Williams to Christina Aguilera to you or myself, and none of us are ever good at everything.
Of course, people who are not too invested in music as a long term career occupation goal see it as, "He plays the guitar and sings country music! Why isn't he so good at the piano?" They don't get it. You need to explain to them, not every Olympic gymnast is a star basketball player because, like sports, music is so different, you cannot be good at everything you ever do. The pressure is on way too much. And, if you are someone who believes people have to be good at everything and don't understand much about pursuing music, please cut people a break.
Mastering anything takes a lot of time. When you divide your time mastering the guitar, piano, voice, violin, cello, tuba, clarinet, and everything, you will run out of steam until you don't really master anything, or you might only play well and not compose good tunes or write good lyrics. Some people are only good at composing and others good at lyrics. Don't feel pressured to be good at all of it.
There is no shame in letting someone else write your lyrics. Myself, I primarily want to do film scores, but if ever I were serious about doing a rock album or something along that, I would probably want to sing someone else's song lyrics. So what? Fans always get crazy about someone writing his or her own lyrics as if that represents someone's lack of talent or flaws. My strength is not in writing lyrics or most kinds of creative writing. I am most confident with scripts as they are straight to the point.
You are fine. Only machines do things perfectly – and you cannot be a machine to create amazing music. You need a strong personality and, hating to sound cliched, soul to write any genre.