vacuuming taking long time for pg_attribute

Hello Experts!

The PgSQL version is 16 and it runs in Cloud SQL managed by GCP.

Problem was that we were unable to conveniently get the object details in
the schema browser (within the Cloud SQL Studio) as it was getting timeout
again and again. Several application jobs start to fail. Eventually we
found that pg_catalog.pg_attribute was having tons of dead tuples. While
vacuum on this took several hours, the problem got resolved eventually.
Command ran: vacuum pg_attribute;

I would like to understand how this issue can be prevented. We do have
autovacuum ON and I could see the last vacuum on this table was just about
30hrs back.

Appreciate any suggestions.

Regards
Siraj