Irrespective of what others may have said before:
Maybe you are one of the people who just "don't have it"? 90% of all musicians never write anything remotely unique and many never even write at all. If you struggle so much, maybe you are just not made to be a songwriter. There's nothing wrong with that and it's actually liberating to know/accept it.
I don't want to sound discouraging, but I don't have the ability to understand tax law. Others may not have the ability to write music. It's normal.
Maybe you are just too critical of your own stuff and give up too easily. Maybe you just need to force it. If you got an idea, stick with it and finish that goddamn song, no matter how much you think it's a rip-off. Then play it to other people. Maybe you are just over-criticizing yourself and others think it's the awesomest shit ever. Maybe you don't write anything unique because your "unique" attempts are just crap and the "not-so-unique" ideas are actually listenable songs (cause they are not as "far out" or "weird")? Also: If you don't finish anything, you won't find out.
I have been writing songs for 20 years, most of which are ANYTHING but "unique" or "original". Some are just straight rips. Over these 20 years I think I averaged about 50 songs per year (do the math, that is 1000 songs in my lifetime so far!). Some of them I never record. Some I just sing into my iPhone and never listen to them again. My phone, harddrive and even old 4-track tapes are full of riffs, beats, ideas that are called "rock idea 15". Some of them are utter shit. About 20-30 get fully produced every year and 10-20 get officially released. That's only 20% of the songs I finish writing. And I am not even counting the 4-bar ideas here, just the fully written songs.
Music is 10% inspiration, 90% perspiration, but most musicians think it's all "play" and some "divine gift" which is frankly bullshit. I recommend buying books on pop-songwriting. They teach you a lot that can be used for any other style too.
Hope this doesn't come across as harsh/condescending, because it isn't meant to be. It's just very difficult for me to phrase it differently