It's very hard to isolate load from different use cases, use a mixture of different technologies or combine batch, event driven and request/response paradigms within a monolith though.
I think certain things are easier to change in a monolith, where as other things are easier to change in a service based design. Depends what mistakes you've made along the way or how the spec/environment changes.
Similarly, A microservices/SOA architecture can fail to break down their domain into good boundaries and abstractions. I've seen this happen a lot.
It's a lot harder to fix bad microservices than to fix a bad monolith