Just what your coworkers said, it's hard to maintain.

It still has it's application but it's quite hard to ultimately work with. For example, if something throws an exception, if you didn't setup the pipeline correctly it's stupidly simple to simply silently drop the exception all together.

And even when you haven't done that, it can be really difficult to understand why an exception has happened. You might be able to fairly decently get to the stage in the pipeline where the error came from, but working back to how the inputs got there in the first place can be really difficult.

More traditional programming is just a lot easier to work with. An exception getting thrown gives you a stack trace that gives a pretty clear picture of how you got to where you are at. And, putting in additional contextual information can make diagnosing everything a lot simpler.

I'll also just say, I find Rx (js, java, C#, etc) to be overly complicated in general. I'd suggest just trying some other reactive frameworks to see what I mean. Kotlin's Flow api is pretty good (IMO) and really makes a lot of struggles around learning Rx much easier to grok. I found that a decent part of what made reactive programming hard wasn't the reactive programming but rather Rx's implementation of it.