We're more interested in integrating the tools and ecosystems people are already using in novel ways than we are in being yet another dashboard or visualization tool. Dashboards and visualizations are incredibly valuable but they're just one of the many ways that analytics teams deliver value to the organization. There are a lot of "jobs to be done" for an analytics team and the list isn't getting any shorter.
EDIT: After reading into this more it seems like Quicksight is Amazon's version of Tableau and connects to SPICE which is Amazon's version of a data warehouse. If you prefer Tableau, you can apparently connect that directly to SPICE. If you already have Tableau connected to a data warehouse, this would appear to be a new competitor to the market and wouldn't add anything to your specific setup (beyond Amazon's claims that they will do it better).