Company I worked for decided to build out a new microservice in language Y. The whole company was writing in W and X, but they decided to write the new service in Y. When something goes wrong, or a bug needs fixing, 3 people in the company of over 100 devs know Y. Guess what management is doing.. Re-writing it in X.
If you have background workers (ActiveJobs/Oban for example), these can be on different queues, that you can scale. It's actually really easy to build out a mono-repo system allow for scale.
If you organise your workers into folders based on their purpose (reporting, exporting, ... ), and you're careful about feature flags, you can drastically reduce git-conflicts and CICD issues.