I see two arguments against:
1. Future buildings will be so much better for the environment that increasing costs today for long lasting buildings or having to wait longer for environmentally better buildings is a net negative
2. Old buildings are typically not useful and so we shouldn’t encourage a future full of them (examples: smaller houses in city centres function ok but aren’t well insulated and could reduce total environmental costs of the city if they were replaced with more dense accommodation; many old churches see little use; many old buildings or rooms of them are no longer fit for any efficient purpose and so are wasting resources, eg banks with lots of space for tellers/vaults/deposit boxes or stock exchanges with big trading pits or warehouses which cannot be converted or even the rooms above shops which often seem to be disused. I have also seen other places where good use is still made of old buildings (typically long lived institutions like schools or societies or universities) though perhaps not as efficient use as might be possible. Obviously there are other cultural arguments for keeping old buildings around (but sometimes I worry regulations enforcing this can be too prohibitive, eg freezing an old building that has been changing slowly over many years at the point it becomes protected).
My 95 year old brick house would beg to differ on utility of old buildings. My prior house was over 230 years old and provided 14 years of excellent utility to me.