Support for NodeJS 16 (which has been EOL for almost two years) in AWS CDK was dropped on May 30th.
Here is the relevant blog post: https://aws.amazon.com/blogs/devops/announcing-the-end-of-support-for-node-js-14-x-and-16-x-in-aws-cdk/
Here is the PR implementing it: https://github.com/aws/aws-cdk-cli/pull/565