This is a very important point. I was a songwriter myself in my Protestant life, and the songs that I wrote were arrived at after a long process of improvization. For me, this process did not stop, even after I had something down on paper, and in some cases, even after the song was published. I am sure this is true of the contemporary, guitar-based (Haas/Schutte/etc.) songs that I personally love to hate. Some of those works cannot be sung without changing them (improvising), and that could confuse congregants who are trying to read what’s in the hymnal.
This is one reason why I prefer the older, established hymns.
That’s also what I see with some of those hymns. Of course, it makes sense to have to change some of those hymns to make it easier for the congregation to sing, but if it is improvised so much to the point that it doesn’t match what’s in the hymnal, I believe, only based on the congregations I know, that it defeats the purpose of congregational singing. And not all “contemporary” hymns written in the last 40+ years have difficult rhythms or are problematic in other areas. So whether or not you like them, they are still simple to sing as written in the hymnal. And, as we see with “Lo, How A Rose”, some of the older hymns can also be difficult. Although I also like the hymn, “Comfort, Comfort, Ye My People”, it is difficult for congregational singing due to the rhythms in it. But I believe it was originally composed for choir. They simplified it by taking out the harmonies for the lower voices, but it is still difficult and I would not choose it as a piece for congregation because of it.
To me, it makes more sense to just initially write the music so that it is simple for a congregation or use older hymns that are already simple. Then, if the musicians wants to use it as a solo or instrumental, they can “dress it up”. So much of vocal music and instrumental solo music from the past allowed for this. The initial melody was simple and then the soloist could add fiorature, coloratura, cadenzas, etc. to make it more interesting and show their musical chops. You’d see this a lot in music written in the a-b-a form from the Baroque and Classical periods and even during the early Romantic period, especially for vocal repertoire. It was constant improvisation, within the confines of the music, of course, which was expected and encouraged by many of the composers of the time. And sometimes people’s improvisations completely changed the sound of the original music. But that’s for
solo music, not for hymn music meant for congregation.
Now what I was talking about was more of an extreme, but I have heard similar things with those newer hymns or even the older, established hymns by the musicians. The improvising styles if different from what I mentioned above. Although I can appreciate what they are doing, you just sit there hearing the people around you trying to sing the hymn like they thought it was supposed to be done and then something completely different, yet not what is written in the hymnal being played by the musicians. If the congregation gets thrown off and doesn’t sing, then it again defeat the purpose of congregational singing.