IME, developers who have this philosophy write code that's very difficult to test. And usually that means code that's very difficult to change, because it's tightly-coupled. Tests "feel" brittle and they feel like they're slowing you down because the architectures people build when they don't write test-first make that true. This attitude, IMO, is just an indicator of a skills/experience gap. You haven't built code that is easy to test or worked with code that is easy to test, so your experience tells you something that's not actually true.

Here's a great video that maybe can help you understand https://youtu.be/ln4WnxX-wrw