Well, it seems to me that the first hurdle is that it has to be HEARD. Then, people can decide if they like it enough to listen to it again. In the old days, songs would be shared by individuals or groups or sung by choirs or other entertainers in strictly live performances. New songs had to have determined people singing them in many venues over a long period of time in order for any songs to get a following. Now days, with the advent of sound technology, media, and even social media, new songs and new recording artists can get a following seemingly overnight.
Sheet music has always been a way for songwriters and composers to deliver their music to performing artists and ultimately to the public. But just try to make a living at the craft! The public is fickle and has never been very understanding. They may like the song and want to sing it, but they are not very willing to lay their money down to buy the sheet music for it. And since the invention of the copy machine, composers basically give up control of their music once they write it down, regardless of whether it gets published or not. If it exists in print somewhere, it seems to be free game for anyone. Even with copyright laws in place, only absolutely honest people follow the rules, especially when it comes to choral sheet music..
For a long time, songs were promoted through record producers to the mass market. New songs by new artists were basically chosen and promoted according to the whims of the record producers and the disc jockeys in the various markets. If the song got played enough on the airwaves, it stood a good chance of selling records to the record-buying public. And it went on from there -- radio, television, movies, records, CD's, DVD's, mp3's and so on.
Now there is a change going on involving Social Media. In effect, what social media does, is to take the promoting of songs to the grassroots level again - individuals sharing to other individuals. And the potential audience is unfathomable! There is clearly potential for artists and songwriters and composers who are courageous and tech-savvy enough to promote their own music without the aid or "packaging" of the big business record producers. It may be a very good thing. Time will tell. But then again, as with nearly any intellectual property, the author usually stays in the poorhouse.
But let's be positive! I want to believe that many a new song will be born and will somehow find its audience.