This church building probably costs 100k/month for maintenance and utilities.
If enough people leave, they will get the message very quickly.
It is no doubt maintained by taxes in some way, either on people registered as adherents, or the people as a whole, or both. Given how few Europeans are part of churches, and how many “historical landmark”/”tourist attraction” churches they have, the state is likely to step in somehow to preserve them if a denomination can’t, I would think, and probably has in many cases since the upkeep has to be so high. Another reason to remember that the church is people, not buildings.
5 And as some spake of the temple, how it was adorned with goodly stones and gifts, he said,
6 As for these things which ye behold, the days will come, in the which there shall not be left one stone upon another, that shall not be thrown down. (Luke 21)
1 And as he went out of the temple, one of his disciples saith unto him, Master, see what manner of stones and what buildings are here!
2 And Jesus answering said unto him, Seest thou these great buildings? there shall not be left one stone upon another, that shall not be thrown down. (Mark 13)