Just to play Devil's Advocate and be argumentative, what is the point of testing in production when your development/staging environment is guaranteed to be identical to your production environment?
Is it? I would argue if you have live data in some large amount, you’re not going to be keeping that in sync with your dev environment (and it should be sanitized, which has its own fun oddities at times). I would also argue that your staging environment probably isn’t running the same hardware specs as live. Inevitably you’ll find race conditions, odd data structures and other fun things which simply aren’t apparent on systems prior to live.
In large systems an enormous amount of energy and dev time is wasted in trying to maintain staging/dev environments. Accepting that they won't ever be the same and building out tooling for safe testing/rollouts in prod is a far better use of resources
Another commenter made a good point that in many domains/systems, environment parity is by definition impossible because in production the system spends (non-trivial amounts of) money.