A growing number of types is a canary in the coal mine

I don't really get this: what counts as a feature? What counts as a type?

Let's say you're writing a new microservice in C# or Java, you will probably exceed 7-8 new classes/structs/enums/interfaces with just boilerplate and external data model.

Now if you're adding 7-8 new types for a small 1-2 week feature... yeah you should probably think twice.