Fuzzing random data is fine for development environments, but it won't give you the same scale or statistical significance as production data. Without that you can't really ensure that a change will work reliably in production, without actually deploying to production. Canary deployments can only give you this assurance to a certain degree, and by definition would only cover a subset of the data, so having a traditional staging environment is still valuable.

Not only that, but a staging environment with prod-like data is also useful for running load, performance and E2E tests without actually impacting production servers or touching production data. In all of these cases, anonymizing production data is important as you want to minimize the risk of data leaks, while also avoiding issues that can happen when testing against real production data (e.g. sending emails to actual customers).