>Thats pretty much what a Pull Request is.

Then you have to use email for the review conversation, make the discussion easily available to everyone involved and future devs, track manually which comment refers to which line of the diff due to lack of overlaying, manually ping to warn of updates, rely on manual quoting, no direct information on whether the CI pipeline succeeded...

To me that feels like writing code using only sed. It is possible, but it removes or makes convoluted an absurd degree of regular work.