The point of this devops stuff, as I understand it, is that you've got your deployment automated to the point that you can push a button and it happens. The whole microservices thing depends on your being able quickly to roll out incremental changes.
There isn't, in principle, any reason you can't do the same for a monolithic application - it's just that historically people have done that less frequently and therefore haven't invested in automating the deployment process.
The big issue is really whether your monolithic application is susceptible to automatic testing: if it isn't, then sawing off the bits that are could well make life easier. Whether those bits communicate via the stack or the network is an implementation detail.