I never did it myself, but a friend of mine compares writing code for CICS to AWS lambdas: small and self-contained programs, strung together into a transaction processing system.
I have had to deal with e.g. JCL and from my experience it is a PITA. It's like when you have a bunch of small bash tools, each doing their job well. Then you have a this big script, that calls them and has to glue everything together and is hard to test and understand even though the small bits are all easy.
I admit though that some things are easier - but this is mostly due to architecture. You rely on one big host and one big database. You don't have to deal with a distributed system then. However it also limits the range of business applications that you can build with such a system.
