It's extremely hard to really do TDD and get code that's hard to change. If you persevere with a design that's hard to change, every single change in your failing-test-fix-implementation TDD cycle will make you refactor all your tests, and you'll realise why the design is bad and reduce coupling instead.
What really happens is that people write code, write non-unit "unit" tests for 100% coverage, and then suffer because those non-unit tests are now dependent on more than just what you are trying to test, all of them have some duplication because of it, and any tiny change is now blocked by tests.
What really happens is that people write code, write non-unit "unit" tests for 100% coverage, and then suffer because those non-unit tests are now dependent on more than just what you are trying to test, all of them have some duplication because of it, and any tiny change is now blocked by tests.