We switched to structured logging a while ago and it's very useful. We have used sentry for ages though and that was a bigger improvement. Many hard to debug problems have actually been trivialised by it, due to the context it provides.

This is for a monolithic application though, I dunno how this would scale for microservices.

The goal of logging a single event per request seems very ambitious imo. But maybe there are things out there that make it easier to glom logs onto a single context object easily and transfer it between services.

Honestly though I think you get a lot of the way there if ever structured log line related to a request includes a request id so you can just filter on that.