Jason Gorman's video highlights the problems of excessive use of mocks in testing.
The issues include difficulty in refactoring, dislike for the test suite, and focusing on high coverage over behavior validation.
Instead, Gorman suggests focusing on creating sections of code that have a clear purpose, exposing a public API, and not worrying about the number of classes or functions internally.
The video emphasizes the importance of easily changing the code through proper design and testing.