Interesting thoughts about the false dichotomy "Monoliths versus Microservices": these are just the 2 extremities of a large range of possibilities.
Microservices are not to scale systems to thousands of users/transactions.
It is more of a solution to organizational issues than to application issues: microservices are to scale TEAMS, not systems.
Think of organizations with hundreds of developers in teams that have to deliver at different paces, isolatedly and independently so that one team doesn't impact the other.
Some thought leaders in this area have been recommending to start new projects as centralized systems rather than distributed services/microservices/lambdas.
If you want to scale apps (increase throughput, reduce latency, etc), you don't really need microservices straight away.
You will have to consider these 3 pillars of scalability and then decide:
1. Caching
2. Asynchronicity
3. Load Balancing