Every day appearing new articles promoting microservices and mentioning monolith applications as old fashioned, non-fancy, bad overall, etc.
All these articles silently ignoring one extremely simple, obvious but extremely inconvenient (for those who promotes microservices) fact: monolith is not an architecture.
Monolith is just application packaging option.
Architecture of packaged application can be any, from rusty "Spring Boot+JPA" to reactive clustered nanoservices. Even microservices can be packaged this way easily. Obviously, differences in architecture will result to differences in performance and scalability characteristic of the application. Comparing architecture to packaging option is like comparing sandwiches to lunch boxes.