I'm not against replacing old systems, but this has to happen in incremental steps. This way, if an implementation path doesn't worth the effort, just drop it

I'm not against replacing old systems, but this has to happen in incremental steps. This way, if an implementation path doesn't worth the effort, just drop it and don't spend dozens of months with a full rewrite and realizing that you are spending a week to implement a CRUD for a simple entity. It's even worse when devs are new to the project and have no knowledge of the domain; I've been burned by this, never again. At the end of the day, we are not in the research field, we are payed to fix business problems, to deliver something that brings a business value. Yeah, it's nice to write some really complex software that would make the system a lot more optimized, but we have to deliver it before our bosses are getting tired of excuses and pull the plug. Learned that the hard way.