If your hierarchy exceeds 1GB then you need to break it up somehow into multiple fields, rows, or tables depending on the specific use case.

If your hierarchy for a given node exceeds 1GB Then you almost certainly are using the wrong tool and should consider some kind of graph db.

Hierarchy != graph (although it can)

There are always better tools but that doesn't mean that it is "wrong". For example, S3 is generally a better tool than Postgres for storing files but there are several legitimate use cases where storing the files in the DB is better than S3.