10 instances... wonderful federation
9 instances... horrible centralisation
10,000 instances with 10,000 S3 buckets.. gods perfect federation
10,000 instances with 5,000 S3 Buckets... absolute evil
There are a cohort of fediverse fans that think any change to the fediverse that doesn't grow the number is evil...
Building some kind of shared services, multi-tenanted instances or any kind of de-duplication to lower the total cost of ownership or limiting wasted resources (power, storage, bandwidth, etc) will get you yelled at for "centralising the fediverse".
Touch Grass.