I have asked this question myself and it has been asked ofme. I should point out that in all fairness there has probably not been a time in history when absolutely all music sucked. That being said, some eras tend to have an overabundance of good music while others have relatively dry periods. I guess you could compare it to wine vintages (yes, I know that is nota very scientific comparison but what the hey?).
I first tried to check my bias by seeing if this phenomena could be explained by my preference for music that I first heard when I was twelve years old. For more on this see this article: http://www.slate.com/articles/health_and_science/science/2014/08/musical_nostalgia_the_psychology_and_neuroscience_for_song_preference_and.html
This wasn’t true in my case. I found that when I was 12 I had a very broad and eclectic musical taste, since I had older siblings who listened to music and I was very precocious. Nevertheless, there were musical forms that I wasn’t attracted to as a 12 yr. old, such as acoustic Prewar blues, that I really enjoy now. And even though I had had some limited exposure to jazz, it was not until I was older that I really appreciated the art form. Moreover, I know people older than myself who positively worship punk rock, new wave, and rap and they could never have heard these for the first time in their teens.
What is music anyway? It is a combination of melody, harmony, rhythm, and personality. The first three elements can be analyzed logically, but the third element is very subjective and can sometimes trump the first three. When we are talking about recorded music we could also include the aspect of production values. In my opinion, modern music puts a premium on production values to the exclusion of the other elements of music.
From early folk and blues to early New Orleans rock and roll direct to disc technologies were employed such that production values relied on capturing a great live performance. This sense of urgency forced the performers to give their all to the recording. This paradigm has been greatly reversed in recent times.
Personality is largely missing in contemporary performers. This aspect is very much controlled by expectations of focus groups and marketing departments. This is why there is so much homogeneity within genres. There is also no sense of urgency since” everything can be fixed in the mix”.
In the 1960’s and early 1970’s the record companies were run by cigar chomping old white men who (according to Frank Zappa) would say ‘I don’t know if it will sell, but what the hell?’ and so, we were blessed with experimental musical forms. However, this circumstance soon gave way to hip young white guys who thought that they knew exactly what the kids wanted. These execs decided to give us safe choices rather than creative ones and this is how we ended up with what we have today. Just as in movies and television, in the music business, imitation is the sincerest form of flattery.
thebluze 
A lot of modern music sucks because there is too much emphasis on production quality over originality. The business is forever trying to find something that sounds like something already commercially proven. Successful bands are steered towards there signature sound which they then fear to deviate from because it would upset sales figures, alienate fans. Watching The Foo Fighters Sonic Boundaries, I had to turn it off before the signature sound wore me down. Ultimately it is about business rather than art, Dave Grohl was worried that if one of their songs sounded a little too Country, then the record company would be on the phone the next day. Although Dave is a lovely guy I very much believe the industry helped him out because of the death of Kurt. I would like to see more bands like the early Seattle scene where it was about pushing boundaries, not in terms of sounding clever but by creating a musical energy that connected with people. Even unsigned artists on sound cloud have not captured the spirit of music I have not really found anything except some of the better music from the dubstep genre. My favorite bands at the moment include Daft Punk that although they have been labeled as electronica or French House, they are more like pop or rock it you listen to the riffs that they create. There approach to music is more from a sound design environment rather than rock band line up.
I agree that the early Seattle scene had the spark of something organic, not contrived.
I think this NYT quote about film is relevant: “The movie industry has long embraced broadly appealing spectacles, but now they must also appeal in translation to foreign markets to show their financiers the money. Greed, for lack of a better word, isn’t always good: it results in sequel-ready franchises with less reliance on nuanced English dialogue and more on eye candy.” I think the music industry has a similar problem. Disposable “lifestyle” music and broad appeal is the name of the game. http://www.nytimes.com/2014/12/14/fashion/you-talkin-to-me-the-decline-of-movie-quotes.html
Trevor, that is a valid observation. It is another manifestation of the ignorance that business types have concerning art or history for that matter. They don’t remember that the Beatles became international stars while keeping their Cockney accents and writing very British songs or that Bob Marley became an inspirational figure to millions worldwide despite the fact that he sang of the plight of people from a small island with a distinctly afrocentric viewpoint. Rather than letting the music speak for itself they are always trying to define the next big thing.