This seamlessly integrates with existing Data Warehouse software solutions and Redshift handles everything you'd normally had to configure, import, read, query

This seamlessly integrates with existing Data Warehouse software solutions and Redshift handles everything you'd normally had to configure, import, read, query yourself using RDS; plus it uses S3 to store its backups and let the client restore their datasets from it. So it doesn't compete with it, my understanding is that it might as well utilize both but in a ready made package that integrates with existing data warehousing solutions.