AWS SSO CLI is a secure replacement for using the aws configure sso wizard with a focus on security and ease of use for organizations with many AWS Accounts and/or users with many IAM Roles to assume. It shares a lot in common with aws-vault, but is more focused on the AWS IAM Identity Center use case instead of static API credentials.
AWS SSO CLI requires your AWS account(s) to be setup with AWS IAM Identity Center, which was previously known as AWS Single Sign-On. If your organization is using the older SAML integration (typically you will have multiple tiles in OneLogin/Okta) then this won't work for you.
AWS SSO CLI focuses on making it easy to select a role via CLI arguments or via an interactive auto-complete experience with both automatic and user-defined metadata (tags) and exports the necessary AWS STS Token credentials to your shell environment in a variety of ways. It even supports sharing credentials via the AWS ECS Task IAM Role.
As part of the goal of improving the end-user experience with AWS SSO, it also supports using multiple AWS Web Console sessions and many other quality of life improvements!