I take some issue with the basic thesis.

I don't think you can outright separate the appreciation of music in to two camps, that of the musical content and that of the lyrical content.

Much as in poetry, the sounds and rhythm of the words are an integral part of what makes a good melody.

Hip-hop might actually be the ultimate example of this. Sure, there is content, but it is mainly about the flow of the lyrics. The fact that the author of the post looks to hip-hop as being some kind of example of the decline in musical appreciation just tells me that he is himself is lacking in the ability to properly listen to music.

Jay-Z has amazing flow. Busta Rhymes is a freaking explosion of syncopated beats, as good as swinging as Gene Krupa, but managing to tie lyrics in as well. KRS-One? Snoop? Eminem? They are practically jazz drummers who use their mouths instead of a drum kit.

I would bet the fact that they're talking about drugs, violence, money, women, and what it's like to be poor are the main reasons they turn people off. Most detractors don't want to know that this world exists and sure as hell don't want to have anything to do with it.

Beyond hip-hop, this is an important element to pretty much all music that could be labeled as "good". Sure, the actual language content is important... you're going to connect with more people if you're singing about heartache and love than if you're singing about molecular biology. However, if your lyrics are set to a stale melody, or don't have a rhythmic foundation that inter-plays with the rest of the music, it's not going to sound good, and people are not going to like it.

Vowel sounds are incredibly important. Imagine the lyrics to your favorite song. Now, get rid of the consonants, and listen to the rhythm of the different vowels. More than likely, you'll find a syncopated pattern. There might be an interplay of the "ee" and "ah" sounds, there might be repeated "oo" sounds at the end of every verse, etc. It may be simplistic, but I can guarantee it's there.

There are a number of great songs that have either nonsensical lyrics in them or at least very simplistic content. Led Zeppelin has never been known for their lyrics and are still selling tons of albums every year. "Ob-la-di-ob-la-dah"? "Ma ma ma my sharona"? And I'm just sticking to rock/pop music with these few examples...

Style and fashion, of course, have a lot to do with popular appeal. And these are based on trends, where timing is everything. If The Beatles were to have never existed (and somehow music today ended up where it is without them, which is highly unlikely) and they suddenly emerged, I'm not sure that they would be all over the airwaves. Sure, there would be people who were absolutely smitten with them, but I they are who they are because of a certain time and place. They hit their peak when albums like Pink Floyd's "Piper at the Gates of Dawn" were top 10 albums in the UK. Can you imagine that? Piper? Top 10? That is one weird and crazy album. Actually, I think it got to number 6 on the charts.

There are a lot of elements that go in to music. But they go in to and form a cohesive whole. It is very hard to separate out one element from another and say that this element is more important than another element.

I don't see how you can split lyrics from their musicality.