Yes you can't change the structure, you can't remove original fix and fit etc, without permission, that's what you're maintaining for historical interest, but you can remove and replace your avocado bathroom suite. No one is interested in preserving that. That's not what the listing is for.
As said the whole point is these homes need to remain habitable. If you can't even replace your shite kitchen, then no one would wish to buy them. They'd fall into disrepair and be abandoned. That's not what anyone wants. Look at any listed home on line and they all have modern kitchens and bathrooms, which says it all.
There is always some scaremongering on these threads. Yes you have a responsibility, yes you'd likely be responsible for restoring anything like original doors if ripped out post listing, but putting up wallpaper, painting the walls internally, new flooring ( as long as doesn't damage anything original) replacing your kitchen or bathroom etc, does not require consent.
Thr goverment doesn't want to make it so onerous you can't live in these properties, and have to live with peeling walls, and knackered bathrooms and kitchens. The only way to preserve them for historical interest, is to enable people to want to live in them.