In my experience, a mediocre engineer can build a decent monolith, especially if they're using an opinionated framework (like Ruby on Rails). On the other hand,

In my experience, a mediocre engineer can build a decent monolith, especially if they're using an opinionated framework (like Ruby on Rails). On the other hand, building microservices is much more complex as there are more moving parts and more failure modes, so the mediocre engineer - and even many non mediocre ones - is much more likely to create problems.