There are many issues tied together here, and best perhaps to separate them as best we can. Each would be worthy of its own post, I imagine, but I'm not up to that. I just like the clarity part.
That hymnals need to change and music needs to be updated is hardly up for discussion. Some churches will be able to maintain a niche market of traditional music for a few decades, but will lose a majority of even the children who grow up there. Of those who did not grow up with such music, they will attract none.
It is also true that whatever the change is, some people will not like it. I barely remember the switch to the Pilgrim Hymnal in my childhood Congregational church, probably around 1961, but I remember being in choir in high school in the late 60's and the older members still complaining about it. I forget why, or what color the previous hymnal was, but I recall that "Holy, Holy, Holy" was hymn #1. My wife and I went to a Lutheran Church in the 70's and 80's and liked the Red Hymnal (1962) rather well. The Green hymnal that came in in the 80's was rather PC and chirpy-cheery, but basically okay. As the complaints came in about it, some of the old Swedes would chuckle about how it was the same when they switched from the Black hymnal (Augustana Synod, 1925) years before. Some were more than half-serious when they said they still preferred it. Then, as Covenanters, we were present for the switch from the Red Hymnal to the Blue. Some of their old Swedes still pine for the old Brown Hymnal. (Few pine for the interim softbound Silver, though I liked that reasonably well). Get ahold of one of those denominational hymnals-before-this-one if you doubt the need to update.
More at issue is the quality of what replaces the traditional music. Granted that people will complain anyway. Granted that words become archaic and change subtly in meaning over time. Granted that the emphasis of church thinking from 1850-1950 was not the pinnacle of Christian understanding. Granted that we should be more alert to not offend with our phrasing, however beautiful. I get all that. Much of the new stuff is still crap. I think we are moving to non-hymnal eras, and that's likely a good thing. In an instant communicating world, things go out of fashion so quickly that there really isn't much sense in expensively preserving what we thought was hip in 2000, let alone 1980 or 1960. It is good to preserve much of what has edified and uplifted the saints from 1500-1950. Nothing to be added to that now - keep the best and move on. The current age does not consider the ephemeral nature of its songs to be a negative. Fine. Let's not preserve it between expensive covers then. Leave them available on the net and open to the air and let the best survive - rather like the old days, before the 20th C, actually.
Our attachment to particular songs is often not well-tied to good theology, poetry, or music, but to personal experiences and emotions. There's nothing wrong with that for us personally, but we need to remember that this doesn't make them more valuable for others. And most of that ain't so great, neither. "Twas grace that taught my heart to fear, and grace my fears relieved" may be profound, but many of the rest of the verses are pretty dumb. They scan and rhyme: sun-begun. Still dumb. Or...
3. Sinners, whose love can ne'er forgetAnd that's one of the really good old hymns. Imagine how you are going to bring in a tribe of even very obedient, devout, and intelligent middle-schoolers and try and build a life-changing theology for their future around such hymns.
the wormwood and the gall,
Go spread your trophies at his feet,
and crown him Lord of all.