Fully using PostGres without awareness of Iceberg would require full decoupling, and a translation layer in between (Debezium, etc). That comes with its own problems.
So perhaps some intimacy between the PostGres and Iceberg schemas is a good thing - especially to support transparent schema evolution.
DuckLake and CrunchyBridge both support SQL queries on the backing Iceberg tables. That's a good option. But a big part of the value of Iceberg comes in being able to read using Spark, Flink, etc.