Part of the problem is developers are often too hesitant to delete tests. Tests, like any code, should be deleted when their value is lower than their cost. Tests have maintenance cost like any other code. Plus they add to the time it takes to produce a build.

When making significant changes to implementation of something it's often worth just leaving acceptance tests in place for regression and deleting unit tests and TDDing your new implementation

TDD has turned into a way for devs to 1-up other devs. When testing becomes a discipline of its own with the knowledge of these testing frameworks, something has gone wrong. Tests shouldn't need much more than assert statements, and maybe a little extra.

> in over abundance can lead to inflexibility and debt when your system needs to change.

I hear this argument a lot, and I think it is absolutely incorrect. If tests are hindering your system then you're just doing it wrong. It's like saying "climbing rope is a hindrance for the rock climber, since I have tied gordian knots around my feet and now cannot move."

TLDR doing something badly doesn't mean the thing you have botched is itself bad.

Yes, this is really what I mean by "over abundance". I'm suggesting that excessive application of unit test "fundamentalism" can lead to a variety of problems. A particular manifestation of what you describe as "doing something badly".