Ahh the Ship of Theseus... is it really the same church after all the changes over the centuries?
Possibly depends on the context. If a man loses his arm, is he the same man? You could answer "yes" and "no" depending on the context of the discussion.
I guess it's entirely subjective as well. If it's broadly the same construction but with some minor of even significant changes, but remains on the same site, roughly the same size, and performing the same function, then it could be the same church. Someone else might have a much narrower definition and decide that even updating the internal wiring makes it a different church. That its identity and character is derived from its flaws and its age and its current state of repair/disrepair. Depends what's important to you. The function? The age? The materials? Or just its significance as a landmark?
If you re-roof a church I doubt many would claim it's a different church. That would just be maintenance. Re-roof it with entirely different materials and some might claim it's no longer the same. Some people obsess over small details. Sometimes that's a valid perspective, sometimes it's petty.
It's yet another thing that we can all disagree on