I can think of few better investments than to have a reliable suite of end-to-end tests running as part of your merge pipeline even if they're difficult to set up. Sleep quality improves once you have this in place. Your tests don't have to be brittle or flaky. If your tests are brittle it is definitely a good investment to fix whatever's causing the brittleness rather than accept it as a fact of life. Having the tests run against an isolated data and infrastructure environment without additional noise from shared activity is a good first step.