There are three types of songwriters: mechanical hit makers, talents who can write, and non-talents who think they can write.
Non-Talents Who Think They Can Write
These people are prolific songwriters. They write what they feel and are so sincere, those around them do not have the heart to tell the writer their ears hurt. Real musicians find true inspiration from their attempts at lyric and melody.
Talents Who Can Write
These artists actually write fine lyrics and pleasant music. They write solely from inspiration. Their music will lift your spirits, and occasionally make you think. Their talents are normally relegated to their own living rooms or an occasional party. A few have actually been able to make a living at it. Some have accrued massive fortunes, such as Elton John, Garth Brooks and Willie Nelson. However, a musician who you consider to be a true 'talent who can write' will depend on your musical taste.
Mechanical Hit Makers
These are the professionals. Most started out as one of the above mentioned types, but somewhere along the line they wised up. They learned, either through trial and error or technical training, that with the proper formula one can write profitable music. They use the latest trend, the most recent hip cultural discovery, or Top Ten lockstep for lyrics. Add the prerequisite modern music and you make money. The music producers Stock, Aiken and Waterman became masters of this during the 1980s.
The mechanical hit making process is much the same as the stock market. You can follow the trends and make a living, but the real movers and shakers go out on a limb. They invest on instinct and feeling. They create the trends and have the most to lose or the most to gain. So it is in the music industry.
For all you 'non-talents' out there the advice is to not give up. Once in a while a 'non-talent' makes it big, and some non-talents actually set the standard for the generation which follows.
The 'talents who can write' should keep in mind most of the major trends are set by them. They are the ones that are followed by the money makers. Being first they stand the most to gain, if anyone ever happens to hear them.
Don't be afraid to be mechanical. After all songwriting is very satisfying. Done with the correct formula, it will put food on the table.