As to code quality, the closest I can come to agreeing with you is that I think some people do unit tests ritualistically, not thoughtfully, and those suites can be relatively low in value. That brittleness you describe is often a sign of that. I rarely see that from people doing actual TDD, though.
Where I part ways, though is the notion that an hour of activity X substitutes for an hour of activity Y. For any given fear you have about your code failing, you should pick the testing approach that yields the most risk reduction per unit of effort. I don't think we can externally judge the right choice for a given team and code base. As long as it's reasonably easy for people to write tests at a variety of levels (unit, integration, functional, end-to-end), and as long as they're committed to continuous improvement, I'm inclined to trust that they'll figure out the right mix for their project.
Where I part ways, though is the notion that an hour of activity X substitutes for an hour of activity Y. For any given fear you have about your code failing, you should pick the testing approach that yields the most risk reduction per unit of effort. I don't think we can externally judge the right choice for a given team and code base. As long as it's reasonably easy for people to write tests at a variety of levels (unit, integration, functional, end-to-end), and as long as they're committed to continuous improvement, I'm inclined to trust that they'll figure out the right mix for their project.