A city-wide fire is a negative externality created by irresponsible management. I'd rather such issues be resolved by courts, but can absolutely see the case.
A historical building is effectively a positive externality provided by the owner. The state cannot ethically force you to provide such a thing, nor can it do so without just compensation (Constitution.) The takings clause is very clear on this; you are preserving a building for public benfit, so the only Constitutional way to do it is by acquisition at fair market rates.
I personally agree with you, but the courts typically don't. I'm merely explaining the legal mechanism which began the restrictive creep. Over reaction to the fires of 100+ years ago, plus some insurance industry lobbying.
Some courts have ruled the way you describe, but more have ruled that it's not a legal taking, since no real-property rights are actually lost via conveyance (in the legal, non-moveable property sense). The value of those rights might be reduced, but the right is still yours; it wasn't a legal taking. They view it as being not much different than a bad neighbor bringing down property values.
Personally, I don't think they should even be able to do it via the takings clause. If implemented at all, it should be strictly opt-in, similar to how zoning is initially adopted in new or annexed jurisdiction.
(Also it's not "public benefit", it's "public use". It's often interpreted by courts as public benefit now, but that's something else I disagree with.)
A historical building is effectively a positive externality provided by the owner. The state cannot ethically force you to provide such a thing, nor can it do so without just compensation (Constitution.) The takings clause is very clear on this; you are preserving a building for public benfit, so the only Constitutional way to do it is by acquisition at fair market rates.