Why does all new pop music sound the same?

What I have heard the last 20 yrs does sound more similar to me than not. Which most all of that music is not my cup of joe to begin with. The you tube video seems to make sense.
People relate to things they are familiar with. In the past few decades people have probably been raised without a connection to original music, acoustic instrumentation, creative music, personal ability to play an instrument even simple ones. So maybe that is why they want to hear the same not very good thing over and over. Just my opinion. 

It sounds the same to all of you because you are OLD.  Don't you all remember your parents saying to you "all your music sounds the same".  Old people have been saying that to younger music fans since 1955. New music sounds different to young people.  Your grandmother couldn't tell the difference between Bob Dylan and Bobbie Sherman.  

Musical inbreeding, encouraged by the industry which is convinced that there's a formula based on recent trends.  But there's plenty of good off-mainstream stuff to hear if you do your homework and there's bound to be someone refreshing and good to come along sometime (probably not soon enough) who will be popular.

The generation gap argument is valid, but music was never packaged the way it is now. Look at the artists who top the Billboard charts and tell me they are not part of a manufacturing process by the same hit factories.

I only surfed past Dick Clark's Rockin Eve, but I heard enough to know that this contemporary genre of music sounds like it was written and produced by the same group of music manipulators.
Of course, using certain "hooks" and style has happened before over the years; e.g., disco, but never so tightly controlled and accepted.

There are a few exceptions in this genre like Lady Gaga...I give her props because she writes her own songs and has been formally trained since a very young age.

But there's plenty of good off-mainstream stuff to hear if you do your homework

This is true, but we always had to search to find alternative music.

And yet the high school seniors I teach have a musical knowledge base and listen to a wider variety of artists than my generation ever did at that age.