For instance, a major component of the Protestant Reformation was encouraging congregational singing, and (particularly Calvanist) church composers of the era brought the music of the church much closer to the contemporary "popular" music of the day.
Definitely, but we also need to consider that before the industrial revolution, Christians were limited in their options (most folks were very poor by modern standards, there isn't much diversity in music in general, and there is a comparatively narrow [and at various times, more corrupt] group of people making decisions on theology and music). So we need to consider history, but we don't weight all history evenly--there is such a thing as 'progress', after all.
That's a bold claim that too many people accept without question and about which too few actually consider the implications.
Progress is improvement. It's moving forward. The notion requires accepting the idea that you were at one point behind where you are now or not as developed/complete/refined. That's fine if you are talking about technology or some other mundane topic, but to make that claim in the context of Christianity - a religion ENTIRELY dependent upon the veracity and completeness of the stories and traditions it is based upon - is to call into question the entire faith.
But to imply that from the BEGINNING Christians were incorrect on something as important as sacramental theology and the role of music in sacramental theology is a completely separate claim with severe implications, as I described above.
I realise this is a very personal perspective, but I find a lot of "secular" music better for worship: Hendrix, Led Zep, Guns 'N' Roses, Soundgarden, Hybrid, She, Pendulum, and of course plenty of orchestral and ensemble music from earlier eras. This stuff stirs my soul.
I'm honestly not trying to be edgy here, and I'm well aware that this isn't going to be everyone's (or even the majority's) bag, and I'm definitely not suggesting that Christian music needs to change for my benefit (it really doesn't). That's all totally OK: it's just me saying that after 22 years of being a Christian I know who I am.
We forget that people are extremely varied, there is room for everybody. An infinite God probably doesn't create only ~3 "right" ways of worshipping, living, serving, teaching, etc.
One reason why we Christians argue so much about which hymn to sing, which liturgy to follow, which way to worship is that the commandments teach us to believe that bad liturgy eventually leads to bad ethics. You begin by singing some sappy, sentimental hymn, then you pray some pointless prayer, and the next thing you know you have murdered your best friend.
Counterpoint: Lots of people, especially those who had not-great experiences growing up in the church, tend to go hard in a different direction when they grow up.
In "Blue Like Jazz", Donald Miller talks about how he thinks it would be super cool to belong to a relatively obscure (in the US) denomination like the Greek Orthodox --- that is, unless he had grown up Greek Orthodox. Then he thinks it would be totally lame and predictable.
For those interested in this sort of thing, Minnesota Public Radio's app has an entire streaming channel of choral music.
People that converted without a high-church context gravitate toward a more modern style of worship.
The downside of so much hillsong influence is that it dominates a culture and drowns out other modern styles. I feel like all hillsong songs sound the same.