Microservices, while often sold as solving a technical problem, usually actually solve for a human problem in scaling up an organization. There's two technical problems that microservices purport to solve: modularization (separation of concerns, hiding implementation, document interface and all that good stuff) and scalability (being able to increase the amount of compute, memory and IO to the specific modules that n…
Modules aren't an alternative to microservices in a reasonable way though. And for all modules solve the modularization problem at the code level, they don't really solve modularization at the service level. The main alternative to microservices is monoliths and for many applications I far prefer microservices to monoliths. I want modularization in how I scale my app, I don't want to spin up a whole bunch of servers…
If you have a particular piece of the system that needs to be scaled, you can take that module out when it becomes necessary. You can alter your system such that you deploy the entire codebase but certain APIs are routed to certain boxes, and you can use batch processing patterns with a set of code outside the codebase.
You can have an admin application and a user application, and both of them are monoliths. They may or may not communication using the database or events or APIs.
However, you don't make this on the single bounded context guideline.