Your interpretation of "people and not the building" is pretty unique to Protestantism in the Christian belief, and arguably the central tenet of Methodism. It is absent in much of the history of Christian (and most other monotheistic) beliefs.
I recommend you look at (as an example), what the Catholic Church did since around the conversion of the Romans through to Vatican II. Even when I was a kid (some decades after Vatican II), attending Catholic school and regularly attending mass, the Catholic Church building was considered an incredibly special place by the congregations.
In my school, the chapel (which held a tabernacle), was once used by some well-meaning but incredibly ill-educated pupils to hold a palm reading booth for a school fete fundraiser. When the more traditional Catholics in the faculty found out, they burst in, soaking the pupils and chapel with holy water and latin prayer (first time used in the school since Vatican II! Showed their colours that day!), claiming that to engage in the occult near a tabernacle was an incredibly offensive thing to do, because the space held a tabernacle, end of.
The whole thing about Protestantism is to remove mystery. Research the early history from Luther through the English Tudors and the King James Bible, all the way through to the Mayflower and the reason why they were fleeing Europe to the New World, and you'll see that big and plain. It doesn't mean that a sense of mystery in terms of rituals and rites held in special designated spaces died and went away though, it just means it's less present than it once was.
For many, many people (billions on Earth today), "holy spaces" remain exactly that: consecrated spaces that are in themselves holy regardless of whether a human congregation is present or not. And this is not limited to Christianity either.
As this was a Methodist Church, I suspect most people who used it would consider it "just a building", albeit one with sentimental memories (weddings, funerals, weekly worship), but sure, it's bricks and mortar and balconies and pews and a broken organ. shrug.
It's just that's actually quite an unusual viewpoint on a global scale, for most denominations.
Catholics abandon and sell church buildings all the time. Once you've removed a small handful of sacred items and done the de-consecration-ritual, it is "just a building" to them too.
There are vast numbers of repurposed churches in Catholic countries. Just walk the streets in an Italian city.
I'm not familiar with the specifics for catholics, but it is conceptually not too different from how protestants do it.
With the caveat, best repeated in every post under this article, that of course very strong sentimental feelings can be attached to a church building. You could put a religious dimension on the morality of hurting peoples feelings by destroying or changing a beautiful thing I guess. But, it is not the house itself that is holy in a holy house.
The piece you're missing is de-consecration. A consecrated space is holy whether the people are in it or not, within the Catholic tradition. Yes, you can deconsecrate it, and then it's just a building. However a loaded tabernacle makes it a holy space in the eyes of Catholics even if it's an empty space. It is conceptually very different to Methodism: the entire point of Methodism is to abandon such mysteries.
I'm eastern orthodox so not part of one of the groups you're talking about but we share a lot with catholics so maybe close enough.
The reaction you're talking about with the palm reading seems like it could have mostly been because of the presence of a loaded tabernacle? I mean I doubt they would have been pleased about this without it but lay catholics I know take the tabernacle extremely seriously.
I don't particularly, aesthetically, like to see churches used for secular purposes but if they've been properly desacralized I don't have any strong religious objections.
> "holy spaces" remain exactly that: consecrated spaces that are in themselves holy regardless of whether a human congregation is present or not
This is true but it implies a causality that is backwards I think. Spaces aren't holy because of the consecration, they're holy because of the people that come there to worship together regularly over many years. If they stop doing that the church doesn't immediately "lose its holiness" or whatever but it does change: it becomes a shrine or a relic or maybe just a building.
> The reaction you're talking about with the palm reading seems like it could have mostly been because of the presence of a loaded tabernacle?
Yes, I think the tabernacle was the crux of the issue here.
> Spaces aren't holy because of the consecration, they're holy because of the people that come there to worship together regularly over many years.
That's a more modern, and dare I say, Methodist view of the church. If a space has a tabernacle in it with the body of Christ in it, within the Catholic tradition, that space is holy and consecrated even when there isn't a human soul in the place, because by definition there is a belief that the soul of Christ is in that space.
You can deconsecrate that space and remove that blessed sacrament and then it's just a building, but in the eyes of most Catholics the space itself has a mystery even in the absence of worshipping congregations.
Like I said I'm orthodox and have never been much exposed to protestant theology other than it just being sort of in the air in western secular culture.
I think you'd get interesting answers if you polled lay catholics with a question like "which is more holy, a consecrated but never-used church, or a parish recently desacralized after centuries of regular use."
There's definitely one "correct" answer if you asked a bishop or a catholic theologian. But I have noticed that there is often a big difference between lay religious experience and hierarchically controlled official dogma. A poll a few years ago had less than half of american catholics believing in transubstantiation, for example.