I did that when I was in my early 20s, got taught to use dedicated TST and UAT environments by more experienced engineers, and now in my 40s I'm telling everyone who's willing to listen that isolated testing is nearly worthless.

The amount of issues I can uncover by using telemetry from production is just insane. Any half-way decent APM will have a dashboard view that summarises errors by how often they occur, which is an automatic priority list.

Some teams I tell this to just blink at me slowly and say they only do testing in UAT, and that after "sign off" they don't see any further need for monitoring. It's signed off, you see! Done. Finished. Released. End. Of. Story.