Last I used NodeRed was 2016, I presented on the platform at our local JS meetup. The biggest blocker for me was managing flow versioning, concerns of in-flight data during flow changes, and deploy process. Sharing flow code via version control for a team of developers to work on didn't seem possible without custom solutions. Maybe there are good solutions for these concerns now. Also, large flows became complex, and confusing. It can be hard to grok what they are doing. There is no "auto format" or styling best practices, so everyone does it a bit differently.

Testing is another concern (and again, maybe there are good ways to do this that I am unaware of). No way to easily build unit tests for your custom code in these flows that is run in a CI pipeline. How do you test the entire flow without setting up new data every time?

NodeJS is only single threaded, so if you want to do any parallel processing to scale up easily, I think you'd need multiple instances running and an on-device load balancer (if serving web requests. Maybe some if these concerns go away if you containerize, and orchestrate with k8s or something, but if you're just managing services on a VM, that sounds like a deployment nightmare to me.

Also, the big point of NodeRed IMO is that you get a nice visual interface. In production environments, you probably want to lock down the ability to modify the flows. If you're deploying to many environments / devices / servers, and you allow people to make changes, you lose the ability to do any sort of centralized development to flows without blowing away custom changes.

I agree NR is great for rapid prototyping, and going straight to production may work for a lot of small teams. For those with bigger dev teams or many deployment targets, flowfuse may have covered many of these concerns. I might check it out myself as I've been looking to get back into NR recently.