The reason for this is multifaceted and each point has its pros and cons.
1. The democratization of music and the heavy use of technology has allowed more people to get involved, And while this allows for more opportunities of expression and viewpoints, It does mean there will be many people who can't sing, Can't write, Can't play an instrument (as a way of communicating-think Carlos Santana/Elton John/Jimi Hendrix/Louis Armstrong).
2 The songs reflect our society, Which is fairly shallow with short attention spans.
3. Similar to other industries, Such as the clothing industry, The expectation of quality has declined and the expectation of quantity and "differentness" has increased.
4. An overemphasis on performance and theatrical entertaining. People are no longer satisfied with listening to a performer sing at a concert standing still with an instrument. They need to jump, Be swung out over the audience, Have fireworks, Smoke, And lasers. One doesn't listen to the lyrics or enjoy the depth of melody with so many distractions.
5. I don't believe that profits and money have much to do with the quality of music declining. It is certainly a great motivator, But we created music for thousands of years prior to EMI and Capitol records. If Tupac was told he would never become rich or famous, He would arguably still have written "Dear Mama". If Paul Simon was told he would never become rich or famous, He would arguably still have written "Kathy's Song" and "The Dangling Conversation". While artistry can be motivated by fame and fortune, In its truest form, It is motivated by the desire to communicate an individual's sense of humanity. Writing a song requires as little as a pencil and paper and maybe an instrument, Both of which do not cost much. Listen to Bernice Johnson Reagon et al sing "We Are Climbing Jacobs Ladder". Does that sound motivated by money or fame? This brings me to a side point, Which is, Songs don't have to be both melodically and lyrically brilliant. We Are Climbing Jacobs Ladder and Beethoven's 9th symphony are duds lyrically, But they convey something through their melody, And the former their voices, That is exceptionally rare.
6. Performer "cults of personality" are also a factor. This ties in with point 4, Which is to say, Many "musicians/artists/performers" (whatever they want to call themselves) spend a disproportionate time marketing themselves to be commercially successful than they do creating something intrinsically human.
7. The highly debated lack of technical skill falls into the democratization facet, But I think deserves further emphasis due to the noticeable lack of it in the current music industry. Technical skills can be instrument playing, Singing, And writing. There are those in the music industry that don't play an instrument, Sound tone deaf when they aren't digitally altered, And require a team of writers to create poetry. Is that person an artist/musician/entertainer? This can be argued until the end of the world.
The standards for "quality music" have declined. The songs that we are listening to today is definitely quite different then we used to have. There seems to be very little thought behind the songs anymore with the same lyrics being repeated over and over. I know it makes money but come on.
There are more and more rapper, hip-hop, and pop artist that make music that is just a repetitive chorus. Nas (an old school rapper) fairly recently made a song called, Shuck and Jive about the decline in music in the last few years. This decline is subject of attention for a lot of school old artist.
Yes, the standards for quality music have declined, because today, anyone can produce music. Today, it is so easy for anyone to set up a recorder and digitally record to their computer and then sell it on iTunes. With there being no quality filters up front, the quality of music declines quickly.
I believe the overall standards for quality music has declined, but the music industry has also taken a financial blow with people sharing the music across the Internet. This has led to less investment in music because there is less profit. I think it has more to do with this problem than anything else.
While some people may not like the type of music that is now on the charts, it is still quality music and it is all a matter of opinion. Every era there will be people who dont like the type of music that is in the charts at that time as it isnt what they grew up with or isnt their taste of music but that doesnt make it any lower of a standard.